WorldWideScience

Sample records for electron emission observations

  1. Polar PWI Observations of Chorus Emissions and Electron Acceleration

    Science.gov (United States)

    Sigsbee, K.; Menietti, J. D.; Santolik, O.; Blake, J. B.

    2006-12-01

    Using data from several geomagnetic storms in 1996-1997 when data from the Polar Plasma Wave Investigation (PWI) were available, we investigated the role of whistler mode chorus in accelerating outer radiation belt electrons. The storm time periods examined included the well-studied January 10-14, 1997 event. Possible correlations between chorus emissions observed by the Polar PWI and energetic electrons between 0.8 MeV and 6.4 MeV observed by the Polar Comprehensive Energetic Particle and Pitch Angle Distribution (CEPPAD) experiment will be presented. We will also discuss how the intensity of chorus emissions depends upon magnetic local time (MLT), magnetic latitude, L-shell, and the location of the plasmapause. We will also examine how chorus generation and the related electron acceleration processes depend upon the Kp and Dst geomagnetic activity indices. Results from detailed analysis of individual case studies and event statistics will be presented.

  2. Observation of reduction of secondary electron emission from helium ion impact due to plasma-generated nanostructured tungsten fuzz

    Science.gov (United States)

    Hollmann, E. M.; Doerner, R. P.; Nishijima, D.; Pigarov, A. Yu

    2017-11-01

    Growth of nanostructured fuzz on a tungsten target in a helium plasma is found to cause a significant (~3×) reduction in ion impact secondary electron emission in a linear plasma device. The ion impact secondary electron emission is separated from the electron impact secondary electron emission by varying the target bias voltage and fitting to expected contributions from electron impact, both thermal and non-thermal; with the non-thermal electron contribution being modeled using Monte-Carlo simulations. The observed (~3×) reduction is similar in magnitude to the (~2×) reduction observed in previous work for the effect of tungsten fuzz formation on secondary electron emission due to electron impact. It is hypothesized that the observed reduction results from re-absorption of secondary electrons in the tungsten fuzz.

  3. Polar PWI and CEPPAD observations of chorus emissions and radiation belt electron acceleration: Four case studies

    Science.gov (United States)

    Sigsbee, K.; Menietti, J. D.; Santolík, O.; Blake, J. B.

    2008-11-01

    We investigated the role of whistler-mode chorus in accelerating outer radiation belt electrons during four moderate geomagnetic storms when data from the Polar Plasma Wave Investigation (PWI) were available. The storm time periods we examined included two storms associated with coronal mass ejections (CMEs), the well-studied January 10-13, 1997 International Solar Terrestrial Physics event and the May 12-15, 1997 event. We compared these two storms with two geomagnetically active periods that were not associated with CMEs. Although strong chorus emissions were observed during all four events, the association of electron acceleration with chorus emissions is not clear. During all four events, the Polar Comprehensive Energetic Particle and Pitch Angle Distribution (CEPPAD) experiment observed increases in the fluxes of energetic electrons (0.8electron fluxes above 0.8 MeV that may have been related to the impact of the CME shock wave upon the magnetosphere. The other two events featured more gradual increases in the electron fluxes over a period of several days. The data from these events indicate that the role played by resonant interactions with chorus in accelerating electrons may depend on the upstream solar wind conditions driving the storm.

  4. Photoelectron spectroscopy of hexachloroplatinate-nucleobase complexes: Nucleobase excited state decay observed via delayed electron emission

    Science.gov (United States)

    Sen, Ananya; Matthews, Edward M.; Hou, Gao-Lei; Wang, Xue-Bin; Dessent, Caroline E. H.

    2015-11-01

    We report low-temperature photoelectron spectra of isolated gas-phase complexes of the hexachloroplatinate dianion bound to the nucleobases uracil, thymine, cytosine, and adenine. The spectra display well-resolved, distinct peaks that are consistent with complexes where the hexachloroplatinate dianion is largely intact. Adiabatic electron detachment energies for the hexachloroplatinate-nucleobase complexes are measured as 2.26-2.36 eV. The magnitudes of the repulsive Coulomb barriers (RCBs) of the complexes are all ˜1.7 eV, values that are lower than the RCB of the uncomplexed PtCl62- dianion as a result of charge solvation by the nucleobases. In addition to the resolved spectral features, broad featureless bands indicative of delayed electron detachment are observed in the 193 nm photoelectron spectra of the four clusters. The 266 nm spectra of the PtCl62- ṡ thymine and PtCl62- ṡ adenine complexes also display very prominent delayed electron emission bands. These results mirror recent results on the related Pt(CN)42- ṡ nucleobase complexes [A. Sen et al., J. Phys. Chem. B 119, 11626 (2015)]. The observation of delayed electron emission bands in the PtCl62- ṡ nucleobase spectra obtained in this work, as for the previously studied Pt(CN)42- ṡ nucleobase complexes, is attributed to one-photon excitation of nucleobase-centred excited states that can effectively couple to the electron detachment continuum, producing strong electron detachment. Moreover, the selective, strong excitation of the delayed emission bands in the 266 nm spectra is linked to fundamental differences in the individual nucleobase photophysics at this excitation energy. This strongly supports our previous suggestion that the dianion within these clusters can be viewed as a "dynamic tag" which has the propensity to emit electrons when the attached nucleobase decays over a time scale long enough to allow autodetachment.

  5. A 3D tomographic reconstruction method to analyze Jupiter's electron-belt emission observations

    Science.gov (United States)

    Santos-Costa, Daniel; Girard, Julien; Tasse, Cyril; Zarka, Philippe; Kita, Hajime; Tsuchiya, Fuminori; Misawa, Hiroaki; Clark, George; Bagenal, Fran; Imai, Masafumi; Becker, Heidi N.; Janssen, Michael A.; Bolton, Scott J.; Levin, Steve M.; Connerney, John E. P.

    2017-04-01

    Multi-dimensional reconstruction techniques of Jupiter's synchrotron radiation from radio-interferometric observations were first developed by Sault et al. [Astron. Astrophys., 324, 1190-1196, 1997]. The tomographic-like technique introduced 20 years ago had permitted the first 3-dimensional mapping of the brightness distribution around the planet. This technique has demonstrated the advantage to be weakly dependent on planetary field models. It also does not require any knowledge on the energy and spatial distributions of the radiating electrons. On the downside, it is assumed that the volume emissivity of any punctual point source around the planet is isotropic. This assumption becomes incorrect when mapping the brightness distribution for non-equatorial point sources or any point sources from Juno's perspective. In this paper, we present our modeling effort to bypass the isotropy issue. Our approach is to use radio-interferometric observations and determine the 3-D brightness distribution in a cylindrical coordinate system. For each set (z, r), we constrain the longitudinal distribution with a Fourier series and the anisotropy is addressed with a simple periodic function when possible. We develop this new method over a wide range of frequencies using past VLA and LOFAR observations of Jupiter. We plan to test this reconstruction method with observations of Jupiter that are currently being carried out with LOFAR and GMRT in support to the Juno mission. We describe how this new 3D tomographic reconstruction method provides new model constraints on the energy and spatial distributions of Jupiter's ultra-relativistic electrons close to the planet and be used to interpret Juno MWR observations of Jupiter's electron-belt emission and assist in evaluating the background noise from the radiation environment in the atmospheric measurements.

  6. Non-equilibrium electron energy distribution in oxygen plasma: observation with optical emission spectroscopy

    Science.gov (United States)

    Boffard, John; Ly, Nathaniel; Wang, Shicong; Swee, Colin; Lin, Chun C.; Wendt, Amy

    2017-10-01

    Partially ionized inductively-coupled RF oxygen plasmas are in widespread use for materials processing, and non-invasive diagnostics are of interest for the optimization and control of the degrees of ionization and dissociation. Our initial study involves a 2-5% admixture of argon for optical emission spectroscopy (OES) of the oxygen plasma glow. The Ar 420.1/419.8 nm line intensity ratio, previously used in other mixtures to compute electron temperature, when 35 eV) electrons; the latter is observed under conditions of low power and high pressure in the oxygen plasma. We tentatively attribute the increase in energetic electrons to a transition to capacitive coupling, leading to electron acceleration to high energy in the sheaths adjacent to the powered electrode, which in this system is a spiral flat antenna separated from the plasma by a dielectric window. Investigations of OES methods involving additional species, including other trace rare gases, O, and O2+,to determine oxygen plasma properties such as non-Maxwellian electron energy distributions will also be described. Supported by NSF Grants PHY-1617602 and PHY-1068670.

  7. Observation of electron emission in the nuclear reaction between protons and deuterons

    Science.gov (United States)

    Lipoglavšek, M.; Markelj, S.; Mihovilovič, M.; Petrovič, T.; Štajner, S.; Vencelj, M.; Vesić, J.

    2017-10-01

    Proton-deuteron fusion reaction has been studied using a proton beam with an energy of 260 keV and a deuterium-implanted graphite target. The reaction product, 3He, usually de-excites by γ-ray emission. However, instead of a γ ray, 3He can emit an electron with a discrete energy of 5.6 MeV, due to electron screening in graphite. Such electrons were identified with the ΔE-E technique. The emission of fast electrons shows that electron screening causes the electrons to approach the nuclei during the reaction very closely. Different behavior of nuclear reactions at low and high energies was also demonstrated.

  8. Observation of quasi-periodic frequency sweeping in electron cyclotron emission of nonequilibrium mirror-confined plasma

    CERN Document Server

    Viktorov, M E; Mansfeld, D A; Golubev, S V

    2016-01-01

    Chirping frequency patterns have been observed in the electron cyclotron emission from strongly nonequilibrium plasma confined in a table-top mirror magnetic trap. Such patterns are typical for the formation of nonlinear phase space structures in a proximity of the wave-particle resonances of a kinetically unstable plasma, also known as the "holes and clumps" mechanism. Our data provides the first experimental evidence for acting of this mechanism in the electron cyclotron frequency domain.

  9. Ferroelectric emission studies for electron emission lithography applications.

    Science.gov (United States)

    Yoo, In K; Ryu, Sang O; Suchicital, Carlos T A; Lee, June K; Kim, Byong M; Chung, Chee W

    2003-10-01

    Ferroelectric switching emission, dielectric switching emission, and pyroelectric emission were studied by patterning images on electron resist for electron emission lithography applications. It was observed that the pyroelectric emission is most acceptable for a high throughput 1:1 electron projection lithography application. A 1:1 electron projection lithography was demonstrated by patterning images with line widths of 30 microm and using pyroelectric emission. A degradation of the pyroelectric emission property of the material was observed during repeated heating cycles below the phase-transition temperature of the ferroelectric material. Annealing excursions above the phase transition temperature prevented the degradation of the pyroelectric emitter.

  10. Field emission electronics

    CERN Document Server

    Egorov, Nikolay

    2017-01-01

    This book is dedicated to field emission electronics, a promising field at the interface between “classic” vacuum electronics and nanotechnology. In addition to theoretical models, it includes detailed descriptions of experimental and research techniques and production technologies for different types of field emitters based on various construction principles. It particularly focuses on research into and production of field cathodes and electron guns using recently developed nanomaterials and carbon nanotubes. Further, it discusses the applications of field emission cathodes in new technologies such as light sources, flat screens, microwave and X-ray devices.

  11. Observed Barium Emission Rates

    Science.gov (United States)

    Stenbaek-Nielsen, H. C.; Wescott, E. M.; Hallinan, T. J.

    1993-01-01

    The barium releases from the CRRES satellite have provided an opportunity for verifying theoretically calculated barium ion and neutral emission rates. Spectra of the five Caribbean releases in the summer of 1991 were taken with a spectrograph on board a U.S. Air Force jet aircraft. Because the line of sight release densities are not known, only relative rates could be obtained. The observed relative rates agree well with the theoretically calculated rates and, together with other observations, confirm the earlier detailed theoretical emission rates. The calculated emission rates can thus with good accuracy be used with photometric observations. It has been postulated that charge exchange between neutral barium and oxygen ions represents a significant source for ionization. If so. it should be associated with emissions at 4957.15 A and 5013.00 A, but these emissions were not detected.

  12. Formation of macromolecular lignin in ginkgo xylem cell walls as observed by field emission scanning electron microscopy.

    Science.gov (United States)

    Terashima, Noritsugu; Awano, Tatsuya; Takabe, Keiji; Yoshida, Masato

    2004-01-01

    Formation of macromolecular lignin in ginkgo cell walls. In the lignifying process of xylem cell walls, macromolecular lignin is formed by polymerization of monolignols on the pectic substances, hemicellulose and cellulose microfibrils that have deposited prior to the start of lignification. Observation of lignifying secondary cell walls of ginkgo tracheids by field emission scanning electron microscopy suggested that lignin-hemicellulose complexes are formed as tubular bead-like modules surrounding the cellulose microfibrils (CMFs), and that the complexes finally fill up the space between CMFs. The size of one tubular bead-like module in the middle layer of the secondary wall (S2) was tentatively estimated to be about 16+/-2 nm in length, about 25+/-1 nm in outer diameter, with a wall thickness of 4+/-2 nm; the size of the modules in the outer layer of the secondary wall (S1) was larger and they were thicker-walled than that in the middle layer (S2). Aggregates of large globular modules were observed in the cell corner and compound middle lamella. It was suggested that the structure of non-cellulosic polysaccharides and mode of their association with CMFs may be important factors controlling the module formation and lignin concentration in the different morphological regions of the cell wall.

  13. Electron and ion induced electron emission from metals and insulators

    CERN Document Server

    Steinbatz, M

    2001-01-01

    gradually exposed to oxygen as an experimental probe. The experimental data are fitted with an analytical model, that is able to describe the observed kinetics. The fit parameters give absolute values of sticking probabilities and of surface reaction rates. During oxidation of aluminum and magnesium also spontaneous emission of electrons (exoelectrons) is observed. This effect is quantitatively studied for different oxygen partial pressures. The experimental data also indicate a significant influence of the surface morphology on the exoemission process. An important consequence of atomic collisions in solids is ionization leading to electron ejection from the target atoms with subsequent migration through the solid. A certain fraction of these electrons finally reaches the surface and is ejected into vacuum. A standard measurement of this phenomenon is the observation of the particle (electron, ion) induced electron emission yield g, defined as the average number of ejected electrons per incoming projectile. ...

  14. Observations of VHF emissions from 50-mA electron beam injections in the ionosphere that are associated with beam-induced discharges

    Science.gov (United States)

    Goerke, R. T.; Kellogg, P. J.; Monson, S. J.; Franz, R. C.; Nemzek, R. J.; Anderson, H. R.; Potter, D. W.; Denig, W. F.; Szuszczewicz, E. P.; Earle, G. D.

    1992-01-01

    Results are presented of observations of strong VHF plasma waves with amplitudes in excess of 0.1 mV/m (Hz)1/2 associated with 50 mA electron beam injections in the ionosphere. Data from three swept-frequency receivers carried on two daughter payloads are analyzed to determine the emission spectra of the electron beam for various energies and currents. These results were obtained from the rocket-borne experiment SCEX 3, NASA flight 39.002 UE, launched February 1, 1990. The accelerator payload also carried photometers, which measured luminosity at wavelengths of 391.4 and 380.5 nm. Several times during electron gun activity the measured luminosity increased much faster than proportional to the beam current. This nonlinear increase is evidence that a discharge is occurring in the vicinity of the accelerator payload. It is inferred from the uniform distribution of the luminosity around the accelerator payload that the observed discharge extends significantly outside the beam cylinder.

  15. Scanning probe microscopy and field emission schemes for studying electron emission from polycrystalline diamond

    OpenAIRE

    Chubenko, Oksana; Baturin, Stanislav S.; Baryshev, Sergey V.

    2016-01-01

    The letter introduces a diagram that rationalizes tunneling atomic force microscopy (TUNA) observations of electron emission from polycrystalline diamonds as described in recent publications. The direct observations of electron emission from grain boundary sites by TUNA could indeed be evidence of electrons originating from grain boundaries under external electric fields. At the same time, from the diagram it follows that TUNA and field emission schemes are complimentary rather than equivalen...

  16. A modified ‘NanoSuit®’ preserves wet samples in high vacuum: direct observations on cells and tissues in field-emission scanning electron microscopy

    Science.gov (United States)

    Takaku, Yasuharu; Suzuki, Hiroshi; Kawasaki, Hideya; Ohta, Isao; Ishii, Daisuke; Hirakawa, Satoshi; Tsutsui, Takami; Matsumoto, Haruko; Takehara, Sayuri; Nakane, Chinatsu; Sakaida, Kana; Suzuki, Chiaki; Muranaka, Yoshinori; Kikuchi, Hirotoshi; Konno, Hiroyuki; Shimomura, Masatsugu

    2017-01-01

    Although field-emission scanning electron microscopy (FE-SEM) has proven very useful in biomedical research, the high vacuum required (10−3 to 10−7 Pa) precludes direct observations of living cells and tissues at high resolution and often produces unwanted structural changes. We have previously described a method that allows the investigator to keep a variety of insect larvae alive in the high vacuum environment of the electron microscope by encasing the organisms in a thin, vacuum-proof suit, the ‘NanoSuit®'. However, it was impossible to protect wet tissues freshly excised from intact organisms or cultured cells. Here we describe an improved ‘NanoSuit' technique to overcome this limitation. We protected the specimens with a surface shield enhancer (SSE) solution that consists of glycerine and electrolytes and found that the fine structure of the SSE-treated specimens is superior to that of conventionally prepared specimens. The SSE-based NanoSuit affords a much stronger barrier to gas and/or liquid loss than the previous NanoSuit did and, since it allows more detailed images, it could significantly help to elucidate the ‘real' organization of cells and their functions. PMID:28405375

  17. A modified 'NanoSuit®' preserves wet samples in high vacuum: direct observations on cells and tissues in field-emission scanning electron microscopy.

    Science.gov (United States)

    Takaku, Yasuharu; Suzuki, Hiroshi; Kawasaki, Hideya; Ohta, Isao; Ishii, Daisuke; Hirakawa, Satoshi; Tsutsui, Takami; Matsumoto, Haruko; Takehara, Sayuri; Nakane, Chinatsu; Sakaida, Kana; Suzuki, Chiaki; Muranaka, Yoshinori; Kikuchi, Hirotoshi; Konno, Hiroyuki; Shimomura, Masatsugu; Hariyama, Takahiko

    2017-03-01

    Although field-emission scanning electron microscopy (FE-SEM) has proven very useful in biomedical research, the high vacuum required (10-3 to 10-7 Pa) precludes direct observations of living cells and tissues at high resolution and often produces unwanted structural changes. We have previously described a method that allows the investigator to keep a variety of insect larvae alive in the high vacuum environment of the electron microscope by encasing the organisms in a thin, vacuum-proof suit, the 'NanoSuit®'. However, it was impossible to protect wet tissues freshly excised from intact organisms or cultured cells. Here we describe an improved 'NanoSuit' technique to overcome this limitation. We protected the specimens with a surface shield enhancer (SSE) solution that consists of glycerine and electrolytes and found that the fine structure of the SSE-treated specimens is superior to that of conventionally prepared specimens. The SSE-based NanoSuit affords a much stronger barrier to gas and/or liquid loss than the previous NanoSuit did and, since it allows more detailed images, it could significantly help to elucidate the 'real' organization of cells and their functions.

  18. Direct observation of iron-induced conformational changes of mitochondrial DNA by high-resolution field-emission in-lens scanning electron microscopy.

    OpenAIRE

    Yaffee, M; Walter, P; Richter, C; Müller, M

    1996-01-01

    When respiring rat liver mitochondria are incubated in the presence of Fe(III) gluconate, their DNA (mtDNA) relaxes from the supercoiled to the open circular form dependent on the iron dose. Anaerobiosis or antioxidants fail to completely inhibit the unwinding. High-resolution field-emission in-lens scanning electron microscopy imaging, in concert with backscattered electron detection, pinpoints nanometer-range iron colloids bound to mtDNA isolated from iron-exposed mitochondria. High-resolut...

  19. Introduction to the physics of electron emission

    CERN Document Server

    Jensen, Kevin L

    2018-01-01

    Electron emission is both a fundamental phenomenon and an enabling component that lies at the very heart of modern science and technology. Written by a recognized authority in the field, with expertise in both electron emission physics and electron beam physics, An Introduction to Electron Emission provides an in-depth look at the physics behind thermal, field, photo, and secondary electron emission mechanisms, how that physics affects the beams that result through space charge and emittance growth, and explores the physics behind their utilization in an array of applications. The book addresses mathematical and numerical methods underlying electron emission, describing where the equations originated, how they are related, and how they may be correctly used to model actual sources for devices using electron beams. Writing for the beam physics and solid state communities, the author explores applications of electron emission methodology to solid state, statistical, and quantum mechanical ideas and concepts r...

  20. Electron cyclotron emission diagnostics on KSTAR tokamak.

    Science.gov (United States)

    Jeong, S H; Lee, K D; Kogi, Y; Kawahata, K; Nagayama, Y; Mase, A; Kwon, M

    2010-10-01

    A new electron cyclotron emission (ECE) diagnostics system was installed for the Second Korea Superconducting Tokamak Advanced Research (KSTAR) campaign. The new ECE system consists of an ECE collecting optics system, an overmode circular corrugated waveguide system, and 48 channel heterodyne radiometer with the frequency range of 110-162 GHz. During the 2 T operation of the KSTAR tokamak, the electron temperatures as well as its radial profiles at the high field side were measured and sawtooth phenomena were also observed. We also discuss the effect of a window on in situ calibration.

  1. Electron emission from nanostructured materials

    Science.gov (United States)

    Safir, Abdelilah

    In this dissertation, standardized methods for measuring electron emission (EE) from nanostructured materials are established. Design of an emitter array platform, synthesis and nanomanipulation of different types of are successfully conducted. Preexisting as well as novel nanostructures are examined for possible use as electron point sources. Three main categories of emitters are under evaluation: oxide nanowires, metallic nanowires and carbon based nanomaterials (CBNs). Tungsten oxides nanowires have low work function, then metallic nanowires have high electrical conductivity and abundant number of free electrons at and below their Fermi level and lastly, CBNs have superior electrical, mechanical, chemical and thermal properties. This evaluation is designed to compare and choose among the nanoemitters that are suitable for EE. Simulation through theoretical modeling is provided to optimize the parameters directly or indirectly affecting EE properties. The models are to enhance the emitter's performance through increase the packing density, reduce the field screening effect, lower the turn-on and the threshold electric fields and increase the emission current densities. The current estimations and the modeling of the validity regions where EE types theoretically exist, help to select and fabricate optimum emitters. An assembly consisting of sample substrate, electrical feedthroughs, electrodes, nano/micro-manipulator and insulators are mounted within a vacuum chamber. An ion vacuum pump and a turbo pump are used to reach a vacuum pressure of 10-7 Torr. Two systems are used for EE characterization of nanostructures: bulk and In-situ configurations. The bulk investigation is realized by designing a vacuum chamber and different sample holders that can resist harsh environment as well as high temperature for both FE and TE experiments. In-situ experiments are conducted in the chamber of the scanning electron microscope (SEM), it consists of designing special sample

  2. Emission of Secondary Electrons from Solid Deuterium

    DEFF Research Database (Denmark)

    Sørensen, H.

    1975-01-01

    An experimental facility was built where films of solid deuterium of known thickness could be made and where they could be irradiated with pulsed beams of electrons (up to 3 keV) and light ions (up to 10 keV). Studies of secondary electron emission were made and the secondary electron emission...

  3. Galactic synchrotron emission from astrophysical electrons

    Science.gov (United States)

    Lineros, Roberto A.; Bringmann, Torsten; Donato, Fiorenza

    2012-07-01

    The interaction between the galactic magnetic field and the non-thermal population of electrons is responsible for a large part of the radio sky from 10 MHz up to several GHz. This population is mostly composed of electrons with primary and secondary origin. Cosmic ray propagation models describe their evolution in space and energy, and allow to study the impact on the radio sky in intensity and morphology at different frequencies. We consider different propagation models and test their compatibility with available radio maps. We find models highly consistent both with B/C data, the local electron flux and synchrotron emission observations. The resulting constraints on propagation models could significantly improve prospects for indirect dark matter searches in these channels and, even more so, in antiprotons.

  4. UV and 532 nm Photo-Dissociation of 2-Nitrotoluene: Observation of Electronically-Excited NO; Emission from Carbon (I); N2-NO Energy Transfer; and Stabilization of 2-Nitrotoluene-Ar Clusters

    Science.gov (United States)

    Diez-y-Riega, H.; Eilers, H.

    2012-07-01

    2-nitrotoluene is a taggant used in explosive compounds and also often used as a simulant for nitro-based high explosives. Various spectroscopic techniques focus on the detection of vibrationally excited NO as an indicator for the presence of explosives. We report on the photo-dissociation of 2-nitrotoluene using UV and 532 nm wavelengths. We not only observe vibrationally excited NO in its electronic ground state, but also vibrationally excited NO in its electronic excited state. The photo-dissociation of 2-nitrotoluene leads to the formation of atomic carbon and its emission, overlapping the NO emission, is observed. Energy transfer from laser-excited nitrogen to NO leads to NO emission with long lifetimes. Argon atoms stabilize 2-nitrotoluene molecules and delay their photo-dissociation.

  5. Early Computed Hard X-Ray Emissions from Two-Plasmon-Decay Fast Electrons Not Observed in Experiments Point to Discrepancies in the Two-Plasmon-Decay Source Model

    Science.gov (United States)

    Delettrez, J. A.; Follett, R. K.; Stoeckl, C.; Seka, W.; Matte, J. P.

    2017-10-01

    The temporal source of two-plasmon-decay (TPD) fast-electron transport in the 1-D hydrodynamic code LILAC, based on the measured, integrated hard x-ray (HXR) emission as a function of laser intensity, depends exponentially on the TPD threshold parameter up to about 0.9 and saturates above it. This model, along with LPSE simulations, produces HXR emissions much earlier than observed for certain shots. The amount of early emission depends on the rise time of the drive pulse and varies from a small shoulder to an early peak much larger than measured as the rise time decreases. The cause of this discrepancy could be that faster rise times limit the population of the thermal electron distribution near 10 keV, from which electrons are accelerated by the TPD plasma waves. Electron kinetic simulations will be performed with the Vlasov-Fokker-Planck code FPI to address the issue of the rise time of the 10-keV electron population as a function of the intensity rise time. Another cause could be an 20% overestimate of the threshold parameter from the hydrodynamic conditions that would disappear over time. This material is based upon work supported by the Department of Energy National Nuclear Security Administration under Award Number DE-NA0001944.

  6. Electron Emission from Ultra-Large Area MOS Electron Emitters

    DEFF Research Database (Denmark)

    Thomsen, Lasse Bjørchmar; Nielsen, Gunver; Vendelbo, Søren Bastholm

    2009-01-01

    Ultralarge metal-oxide-semiconductor (MOS) devices with an active oxide area of 1 cm2 have been fabricated for use as electron emitters. The MOS structures consist of a Si substrate, a SiO2 tunnel barrier (~5 nm), a Ti wetting layer (3–10 Å), and a Au top layer (5–60 nm). Electron emission from...

  7. Ion-induced electron emission microscopy

    Science.gov (United States)

    Doyle, Barney L.; Vizkelethy, Gyorgy; Weller, Robert A.

    2001-01-01

    An ion beam analysis system that creates multidimensional maps of the effects of high energy ions from an unfocussed source upon a sample by correlating the exact entry point of an ion into a sample by projection imaging of the secondary electrons emitted at that point with a signal from a detector that measures the interaction of that ion within the sample. The emitted secondary electrons are collected in a strong electric field perpendicular to the sample surface and (optionally) projected and refocused by the electron lenses found in a photon emission electron microscope, amplified by microchannel plates and then their exact position is sensed by a very sensitive X Y position detector. Position signals from this secondary electron detector are then correlated in time with nuclear, atomic or electrical effects, including the malfunction of digital circuits, detected within the sample that were caused by the individual ion that created these secondary electrons in the fit place.

  8. Ferroelectric Electron Emission Principles and Technology

    CERN Document Server

    Riege, H

    1997-01-01

    The spontaneous electrical polarization of ferroelectric materials can be changed either by reversal or by phase transition from a ferroelectric into a non-ferroelectric state or vice versa. If spontaneous polarization changes are induced with fast heat, mechanical pressure, laser or electric field pulses on a submicrosecond time scale, strong uncompensated surface charge densities and related polarization fields are generated, which may lead to the intense self-emission of electrons from the negatively charged free surface areas of the ferroelectric sample. Hence, electron guns can be built with extraction-field-free ferroelectric cathodes, which may be easily separated from the high-field regions of post-accelerating gap structures. The intensity, the energy, the temporal and spatial distribution, and the repetitition rate of the emitted electron beams can be controlled within wide limits via the excitation pulses and external focusing and accelerating electromagnetic fields. The technological advantages an...

  9. EC-5 fifth international workshop on electron cyclotron emission and electron cyclotron heating

    Energy Technology Data Exchange (ETDEWEB)

    Prater, R.; Lohr, J. [eds.

    1985-12-31

    This report contains papers on the following topics: electron cyclotron emission measurements; electron cyclotron emission theory; electron cyclotron heating; gyrotron development; and ECH systems and waveguide development. These paper have been indexed separately elsewhere. (LSP).

  10. Electron cyclotron emission measurements at the stellarator TJ-K

    Energy Technology Data Exchange (ETDEWEB)

    Sichardt, Gabriel; Ramisch, Mirko [Institut fuer Grenzflaechenverfahrenstechnik und Plasmatechnologie, Universitaet Stuttgart (Germany); Koehn, Alf [Max-Planck-Institut fuer Plasmaphysik, Garching (Germany)

    2016-07-01

    Electron temperature (T{sub e}) measurements in the magnetised plasmas of the stellarator TJ-K are currently performed by means of Langmuir probes. The use of these probes is restricted to relatively low temperatures and the measurement of temperature profiles requires the acquisition of the local current-voltage characteristics which limits strongly the sampling rate. As an alternative, T{sub e} can be measured using the electron cyclotron emission (ECE) that is generated by the gyration of electrons in magnetised plasmas. Magnetic field gradients in the plasma lead to a spatial distribution of emission frequencies and thus the measured intensity at a given frequency can be related to its point of origin. The T{sub e} dependence of the intensity then leads to a temperature profile along the line of sight for Maxwellian velocity distributions. A diagnostic system for T{sub e} measurements using ECE is currently being set up at TJ-K. When non-thermal electrons are present the emission spectrum changes dramatically. Therefore, the ECE can also be used to investigate the contribution of fast electrons to previously observed toroidal net currents in TJ-K. Simulations are used to examine the role of electron drift orbits in generating these currents.

  11. Instrumentation and Measurements for Electron Emission from Charged Insulators

    Science.gov (United States)

    Sim, Alec M.

    2005-01-01

    The electron was first discovered in 1898 by Sir John Joseph Thomson and has since been the subject of detailed study by nearly every scientific discipline. At nearly the same time Heinrich Rudolf Hertz conducted a series of experiments using cathode tubes, high potentials and ultraviolet light. When applying a large potential to a cathode he found that an arching event across the metal plates would occur. In addition, when shining an ultraviolet light on the metal he found that less potential was required to induce the spark. This result, taken together with other electrical phenomena brought about by the shining of light upon metal and was eventually termed the photoelectric effect. The work of Thomson and Hertz represent the beginning of electron emission studies and a body of ideas that pervade nearly all aspects of physics. In particular these ideas tell us a great deal about the nature of physical interactions within solids. In this thesis we will focus on the emission of electrons induced by an incident electron source over a range of energies, in which one can observe changes in emitted electron flux and energy distribution. In particular, when energetic particles impinge on a solid they can impart their energy, exciting electrons within the material. If this energy is sufficient to overcome surface energy barriers such as the work function, electron affinity or surface charge potential, electrons can escape from the material. The extent of electron emission from the material can be quantified as the ratio of incident particle flux to emitted particle flux, and is termed the electron yield.

  12. Explosive electron emission from flat Ge crystals

    Energy Technology Data Exchange (ETDEWEB)

    Porshyn, Vitali; Mingels, Stephan; Luetzenkirchen-Hecht, Dirk; Mueller, Guenter [University of Wuppertal (Germany)

    2016-07-01

    During the search for photo-induced field emission from flat semiconductors, which might provide high brightness electron beams, we have found with our new ultra-high vacuum measurement system explosive electron emission (EEE) from n-doped Ge crystals resulting in high current pulses of ∝100 A and ∝4 ns duration. This effect reproducibly appears in a narrow photon energy range of 3.2-3.6 eV with a quantum efficiency of up to 20%. Moreover, the EEE current does not depend on the surface field but on the extraction voltage (500-3000 V). EEE is a well known plasma-induced effect for locally heated metals resulting in a crater-like destruction of the surface. For Ge, however, it appears at a factor of 20 lower power density (0.3 MW/cm{sup 2}) of the pulsed laser, and each current pulse forms a new crater of ∝10 μm size. The measured EEE spectra show a similar FWHM (< 1 eV) as photo emitted electrons. Potential applications, e.g. in microwave tubes or gyrotrons, will be discussed.

  13. Secondary electron emission characteristics of oxide electrodes in flat electron emission lamp

    Directory of Open Access Journals (Sweden)

    Chang-Lin Chiang

    2016-01-01

    Full Text Available The present study concerns with the secondary electron emission coefficient, γ, of the cathode materials used in the newly developed flat electron emission lamp (FEEL devices, which essentially integrates the concept of using cathode for fluorescent lamp and anode for cathode ray tube (CRT to obtain uniform planar lighting. Three different cathode materials, namely fluorine-doped tin oxide (FTO, aluminum oxide coated FTO (Al2O3/FTO and magnesium oxide coated FTO (MgO/FTO were prepared to investigate how the variations of γ and working gases influence the performance of FEEL devices, especially in lowering the breakdown voltage and pressure of the working gases. The results indicate that the MgO/FTO bilayer cathode exhibited a relatively larger effective secondary electron emission coefficient, resulting in significant reduction of breakdown voltage to about 3kV and allowing the device to be operated at the lower pressure to generate the higher lighting efficiency.

  14. Secondary electron emission characteristics of oxide electrodes in flat electron emission lamp

    Energy Technology Data Exchange (ETDEWEB)

    Chiang, Chang-Lin, E-mail: CLChiang@itri.org.tw; Li, Chia-Hung [Green Energy and Environment Research Laboratories, Industrial Technology Research Institute, 195, Sec. 4, Chung Hsing Road, Chutung 310, Taiwan (China); Department of Electrophysics, National Chiao Tung University, 1001 Ta Hsueh Road, Hsinchu 300, Taiwan (China); Zeng, Hui-Kai [Department of Electronic Engineering, Chung Yuan Christian University, 200 Chung Pei Road, Chung Li 320, Taiwan (China); Li, Jung-Yu, E-mail: JY-Lee@itri.org.tw; Chen, Shih-Pu; Lin, Yi-Ping [Green Energy and Environment Research Laboratories, Industrial Technology Research Institute, 195, Sec. 4, Chung Hsing Road, Chutung 310, Taiwan (China); Hsieh, Tai-Chiung; Juang, Jenh-Yih, E-mail: jyjuang@cc.nctu.edu.tw [Department of Electrophysics, National Chiao Tung University, 1001 Ta Hsueh Road, Hsinchu 300, Taiwan (China)

    2016-01-15

    The present study concerns with the secondary electron emission coefficient, γ, of the cathode materials used in the newly developed flat electron emission lamp (FEEL) devices, which essentially integrates the concept of using cathode for fluorescent lamp and anode for cathode ray tube (CRT) to obtain uniform planar lighting. Three different cathode materials, namely fluorine-doped tin oxide (FTO), aluminum oxide coated FTO (Al{sub 2}O{sub 3}/FTO) and magnesium oxide coated FTO (MgO/FTO) were prepared to investigate how the variations of γ and working gases influence the performance of FEEL devices, especially in lowering the breakdown voltage and pressure of the working gases. The results indicate that the MgO/FTO bilayer cathode exhibited a relatively larger effective secondary electron emission coefficient, resulting in significant reduction of breakdown voltage to about 3kV and allowing the device to be operated at the lower pressure to generate the higher lighting efficiency.

  15. Secondary electron emission characteristics of oxide electrodes in flat electron emission lamp

    Science.gov (United States)

    Chiang, Chang-Lin; Zeng, Hui-Kai; Li, Chia-Hung; Li, Jung-Yu; Chen, Shih-Pu; Lin, Yi-Ping; Hsieh, Tai-Chiung; Juang, Jenh-Yih

    2016-01-01

    The present study concerns with the secondary electron emission coefficient, γ, of the cathode materials used in the newly developed flat electron emission lamp (FEEL) devices, which essentially integrates the concept of using cathode for fluorescent lamp and anode for cathode ray tube (CRT) to obtain uniform planar lighting. Three different cathode materials, namely fluorine-doped tin oxide (FTO), aluminum oxide coated FTO (Al2O3/FTO) and magnesium oxide coated FTO (MgO/FTO) were prepared to investigate how the variations of γ and working gases influence the performance of FEEL devices, especially in lowering the breakdown voltage and pressure of the working gases. The results indicate that the MgO/FTO bilayer cathode exhibited a relatively larger effective secondary electron emission coefficient, resulting in significant reduction of breakdown voltage to about 3kV and allowing the device to be operated at the lower pressure to generate the higher lighting efficiency.

  16. Electron beam injection during active experiments. I - Electromagnetic wave emissions

    Science.gov (United States)

    Winglee, R. M.; Kellogg, P. J.

    1990-01-01

    The wave emissions produced in Echo 7 experiment by active injections of electron beams were investigated to determine the properties of the electromagnetic and electrostatic fields for both the field-aligned and cross-field injection in such experiments and to evaluate the sources of free energy and relative efficiencies for the generation of the VLF and HF emissions. It is shown that, for typical beam energies in active experiments, electromagnetic effects do not substantially change the bulk properties of the beam, spacecraft charging, and plasma particle acceleration. Through simulations, beam-generated whistlers; fundamental z-mode and harmonic x-mode radiation; and electrostatic electron-cyclotron, upper-hybrid, Langmuir, and lower-hybrid waves were identified. The characteristics of the observed wave spectra were found to be sensitive to both the ratio of the electron plasma frequency to the cyclotron frequency and the angle of injection relative to the magnetic field.

  17. Study of luminous emissions associated to electron emissions in radiofrequency cavities; Etude des emissions lumineuses associees aux emissions electroniques dans les cavites hyperfrequences

    Energy Technology Data Exchange (ETDEWEB)

    Maissa, S

    1996-11-26

    This study investigates luminous emissions simultaneously to electron emissions and examines their features in order to better understand the field electron emission phenomenon. A RF cavity, operating at room temperature and in pulsed mode, joined to a sophisticated experimental apparatus has been especially developed. The electron and luminous emissions are investigated on cleaned or with metallic, graphitic and dielectric particles contaminated RF surfaces in order to study their influence on these phenomena. During the surface processing, unstable luminous spots glowing during one RF pulse are detected. Their apparition is promoted in the vicinity of the metallic particles or scratches. Two hypotheses could explain their origin: the presence of micro-plasmas associated to electronic explosive emission during processing or the thermal radiation of the melted metal during this emission. Stable luminous spots glowing during several RF pulses are also detected and appear to increase on RF surfaces contaminated with dielectric particles, leading to strong and explosive luminous emissions. Two interpretations are considered: the initiation of surface breakdowns on the dielectric particles or the heating by the RF field at temperatures sufficiently intense to provoke their thermal radiation then their explosion. Finally a superconducting cavity has been adapted to observe luminous spots, which differ from the former ones bu their star shape and could be associated to micro-plasmas, revealed by the starbursts observed on superconducting cavity walls. (author) 102 refs.

  18. Charging regime of pur spinel studied by secondary electron emission

    Energy Technology Data Exchange (ETDEWEB)

    Boughariou, A., E-mail: aicha_boughariou@yahoo.fr [LaMaCoP, Université de Sfax pour le sud, Faculté des Sciences, 3038 Sfax (Tunisia); Kallel, A. [LaMaCoP, Université de Sfax pour le sud, Faculté des Sciences, 3038 Sfax (Tunisia); Blaise, G. [LPS, Université Paris-Sud XI, Batiment 510, Orsay 91405 (France)

    2013-04-01

    Insulators are currently used in high technological devices. They are chosen because of their electrical properties of insulation and their thermal properties. It is well known that the presence of space charge in an insulator is correlated with an electric breakdown. Charging phenomena of insulator were studied thanks to a scanning electron microscope (SEM) which allows the injection of few electrons doses in a large domain of energies. SEM permits also the measurements of the secondary electron emission and the induced current created in the sample holder by the charges generated in the sample. The results showed that the secondary electron emission yield (SEE) σ is a very sensitive parameter to characterize the charging state of an insulator. In this work we investigate the charging effect of insulator surfaces like pur spinel (MgAl{sub 2}O{sub 4}) during 1.1, 5 and 15 keV. The results showed that the fundamental parameter controlling the charging kinetic is the current density J{sub 0}. At low energies 1.1 and 5 keV, two different kinds of self-regulated regime (σ=1) were observed as a function of current density. At 15 keV energy, the electron emission appears to be stimulated by the current density, due to the Poole–Frenkel effect.

  19. Extraction of terahertz emission from a grating-coupled high-electron-mobility transistor

    Institute of Scientific and Technical Information of China (English)

    Zhou Yu; Li Xinxing; Tan Renbing; Xue Wei; Huang Yongdan; Lou Shitao; Zhang Baoshun; Qin Hua

    2013-01-01

    In a grating-coupled high-electron-mobility transistor,weak terahertz emission with wavelength around 400μm was observed by using a Fourier-transform spectrometer.The absolute terahertz emission power was extracted from a strong background blackbody emission by using a modulation technique.The power of terahertz emission is proportional to the drain-source current,while the power of blackbody emission has a distinct relation with the electrical power.The dependence on the drain-source bias and the gate voltage suggests that the terahertz emission is induced by accelerated electrons interacting with the grating.

  20. On the Computation of Secondary Electron Emission Models

    OpenAIRE

    Clerc, Sebastien; Dennison, JR; Hoffmann, Ryan; Abbott, Jonathon

    2006-01-01

    Secondary electron emission is a critical contributor to the charge particle current balance in spacecraft charging. Spacecraft charging simulation codes use a parameterized expression for the secondary electron (SE) yield delta(Eo) as a function of the incident electron energy Eo. Simple three-step physics models of the electron penetration, transport, and emission from a solid are typically expressed in terms of the incident electron penetration depth at normal incidence R(Eo) and the mean ...

  1. Correlation electron cyclotron emission diagnostic in TCV

    Science.gov (United States)

    Fontana, M.; Porte, L.; Molina Cabrera, P.

    2017-08-01

    The correlation electron cyclotron emission diagnostic of tokamak à configuration variable has recently been upgraded. It now has the choice of three lines of sight: two horizontal lines placed on the low field side of the vessel, perpendicular to the magnetic field, and a dual-axis steerable antenna. The polarization of the radiation collected by the latter can be rotated using a universal polarizer situated in the transmission line. This line is also shared with a reflectometry system, allowing simultaneous measurements of temperature and density fluctuations in the same plasma volumes. When using this line, it is possible to choose between two dedicated front ends characterized by different local oscillator frequencies, adding flexibility in the choice of the plasma region to be studied. The intermediate frequency section is now equipped with six frequency tunable YIG filters allowing the study of turbulence properties in a wide range of radial positions. When studying fluctuations over the whole video bandwidth, the minimum detectable fluctuation level is δ Te/Te˜0.5 % . The new system has been used to measure electron temperature fluctuations over a large fraction of the plasma profiles in a series of plasmas with triangularity varying from 0.6 to -0.6 but comparable collisionality profiles.

  2. Intense Harmonic Emissions Observed in Saturn's Ionosphere

    Science.gov (United States)

    Sulaiman, A. H.; Kurth, W. S.; Persoon, A. M.; Menietti, J. D.; Farrell, W. M.; Ye, S.-Y.; Hospodarsky, G. B.; Gurnett, D. A.; Hadid, L. Z.

    2017-12-01

    The Cassini spacecraft's first Grand Finale orbit was carried out in April 2017. This set of 22 orbits had an inclination of 63° with a periapsis grazing Saturn's ionosphere, thus providing unprecedented coverage and proximity to the planet. Cassini's Radio and Plasma Wave Science instrument repeatedly detected intense electrostatic waves and their harmonics near closest approach in the dayside equatorial topside ionosphere. The fundamental modes were found to both scale and trend best with the H+ plasma or lower hybrid frequencies, depending on the plasma composition considered. The fine-structured harmonics are unlike previous observations, which scale with cyclotron frequencies. We explore their generation mechanism and show strong evidence of their association with whistler mode waves, consistent with theory. The possibility of Cassini's presence in the ionosphere influencing the resonance and harmonics is discussed. Given their link to the lower hybrid frequency, these emissions may offer clues to constraining Saturn's ionospheric properties.

  3. Deducing Electron Properties from Hard X-Ray Observations

    Science.gov (United States)

    Kontar, E. P.; Brown, J. C.; Emslie, A. G.; Hajdas, W.; Holman, G. D.; Hurford, G. J.; Kasparova, J.; Mallik, P. C. V.; Massone, A. M.; McConnell, M. L.; hide

    2011-01-01

    X-radiation from energetic electrons is the prime diagnostic of flare-accelerated electrons. The observed X-ray flux (and polarization state) is fundamentally a convolution of the cross-section for the hard X-ray emission process(es) in question with the electron distribution function, which is in turn a function of energy, direction, spatial location and time. To address the problems of particle propagation and acceleration one needs to infer as much information as possible on this electron distribution function, through a deconvolution of this fundamental relationship. This review presents recent progress toward this goal using spectroscopic, imaging and polarization measurements, primarily from the Reuven Ramaty High Energy Solar Spectroscopic Imager (RHESSI). Previous conclusions regarding the energy, angular (pitch angle) and spatial distributions of energetic electrons in solar flares are critically reviewed. We discuss the role and the observational evidence of several radiation processes: free-free electron-ion, free-free electron-electron, free-bound electron-ion, photoelectric absorption and Compton backscatter (albedo), using both spectroscopic and imaging techniques. This unprecedented quality of data allows for the first time inference of the angular distributions of the X-ray-emitting electrons and improved model-independent inference of electron energy spectra and emission measures of thermal plasma. Moreover, imaging spectroscopy has revealed hitherto unknown details of solar flare morphology and detailed spectroscopy of coronal, footpoint and extended sources in flaring regions. Additional attempts to measure hard X-ray polarization were not sufficient to put constraints on the degree of anisotropy of electrons, but point to the importance of obtaining good quality polarization data in the future.

  4. The microstructure of alkaline earth oxide electron emission material

    Science.gov (United States)

    Blonski, Robert Peter

    Alkaline earth oxide coatings are used to lower the work-function of thermionic cathodes. Due to their extensive use in electronic vacuum tubes, significant efforts went into the study of their physics and chemistry. Currently, alkaline earth oxide coated tungsten filaments are used as thermionic cathodes in fluorescent discharge lamps. Elizabeth Grey, in 1951, published an emission current phase diagram of the BaO:SrO:CaO system which demonstrated that the central area of this composition space yielded eight times the emission current than compositions nearer the edges of the phase diagram. There has never been an explanation of why the central compositional area of the BaO:SrO:CaO system has a much lower work-function than other compositions. The objective of this thesis was to determine whether there are any microstructural features present in the central area of the BaO:SrO:CaO compositional space that could account for the improved electron emission of these compositions. Triple alkaline earth oxide compositions were examined via transmission electron microscopy of alkaline earth oxide electron emission material from fluorescent discharge lamp cathodes, and via X-ray diffraction from conventionally fired samples. In both cases, ordered phases with cation occupancy similar to hexagonal perovskite phases were identified. The hexagonal structures observed in this thesis study, and the fcc rock-salt structure that was expected, are all the result of ordered stacking of close-packed ions in the hexagonal c-direction. Whereas the fcc structure has a three layer repeat sequence, the ordered alkaline earth oxide phases observed in this study appear to have an eight layer repeat sequence. The effect of the observed super-lattice ordering on the band-structure of the alkaline earth oxide electron emission material may explain the low work-function of mixed akaline earth oxide coated cathodes. The behavior of both barium oxide and strontium oxide was also investigated

  5. Simulating Electron Cyclotron Maser Emission for Low Mass Stars

    Science.gov (United States)

    Llama, Joe; Jardine, Moira

    2018-01-01

    Zeeman-Doppler Imaging (ZDI) is a powerful technique that enables us to map the large-scale magnetic fields of stars spanning the pre- and main-sequence. Coupling these magnetic maps with field extrapolation methods allow us to investigate the topology of the closed, X-ray bright corona, and the cooler, open stellar wind.Using ZDI maps of young M dwarfs with simultaneous radio light curves obtained from the VLA, we present the results of modeling the Electron-Cyclotron Maser (ECM) emission from these systems. We determine the X-ray luminosity and ECM emission that is produced using the ZDI maps and our field extrapolation model. We compare these findings with the observed radio light curves of these stars. This allows us to predict the relative phasing and amplitude of the stellar X-ray and radio light curves.This benchmarking of our model using these systems allows us to predict the ECM emission for all stars that have a ZDI map and an observed X-ray luminosity. Our model allows us to understand the origin of transient radio emission observations and is crucial for disentangling stellar and exoplanetary radio signals.

  6. Effect of Secondary Electron Emission on Electron Cross-Field Current in E×B Discharges

    Energy Technology Data Exchange (ETDEWEB)

    Yevgeny Raitses, Igor D. Kaganovich, Alexander Khrabrov, Dmytro Sydorenko, Nathaniel J. Fisch and Andrei Smolyakov

    2011-02-10

    This paper reviews and discusses recent experimental, theoretical, and numerical studies of plasma-wall interaction in a weakly collisional magnetized plasma bounded with channel walls made from different materials. A lowpressure ExB plasma discharge of the Hall thruster was used to characterize the electron current across the magnetic field and its dependence on the applied voltage and electron-induced secondary electron emission (SEE) from the channel wall. The presence of a depleted, anisotropic electron energy distribution function with beams of secondary electrons was predicted to explain the enhancement of the electron cross-field current observed in experiments. Without the SEE, the electron crossfield transport can be reduced from anomalously high to nearly classical collisional level. The suppression of SEE was achieved using an engineered carbon velvet material for the channel walls. Both theoretically and experimentally, it is shown that the electron emission from the walls can limit the maximum achievable electric field in the magnetized plasma. With nonemitting walls, the maximum electric field in the thruster can approach a fundamental limit for a quasineutral plasma.

  7. Observations of Obliquely Propagating Electron Bernstein Waves

    DEFF Research Database (Denmark)

    Armstrong, R. J.; Juul Rasmussen, Jens; Stenzel, R. L.

    1981-01-01

    Plane electron Bernstein waves propagating obliquely to the magnetic field are investigated. The waves are excited by a plane grid antenna in a large volume magnetoplasma. The observations compare favorably with the predictions of the linear dispersion relation.......Plane electron Bernstein waves propagating obliquely to the magnetic field are investigated. The waves are excited by a plane grid antenna in a large volume magnetoplasma. The observations compare favorably with the predictions of the linear dispersion relation....

  8. Diverse electron-induced optical emissions from space observatory materials at low temperatures

    Science.gov (United States)

    Dennison, J. R.; Evans Jensen, Amberly; Wilson, Gregory; Dekany, Justin; Bowers, Charles W.; Meloy, Robert

    2013-09-01

    Electron irradiation experiments have investigated the diverse electron-induced optical and electrical signatures observed in ground-based tests of various space observatory materials at low temperature. Three types of light emission were observed: (i); long-duration cathodoluminescence which persisted as long as the electron beam was on (ii) short-duration (fiberglass-epoxy composites, and macroscopically-conductive carbon-loaded polyimides). We conclude that electron-induced optical emissions resulting from interactions between observatory materials and the space environment electron flux can, in specific circumstances, make significant contributions to the stray light background that could possibly adversely affect the performance of space-based observatories.

  9. First results of electron cyclotron emission measurements at the GDT magnetic mirror

    CERN Document Server

    Shalashov, A G; Gospodchikov, E D; Lubyako, L V; Yakovlev, D V; Bagryansky, P A

    2016-01-01

    This paper summarizes the results of experiments on electron cyclotron emission (ECE) measurements at the fundamental harmonic recently performed at the axially symmetric magnetic mirror device GDT (Budker Institute, Novosibirsk). New ECE diagnostics is installed to facilitate the successful electron cyclotron resonance heating experiment and operates in the vicinity of the heating frequency of 54.5 GHz. Besides expected emission of thermal electrons, a clearly resolved non-thermal ECE is observed indicating the presence of suprathermal electrons driven by high-power microwave heating. The particulars of plasma emission are studied experimentally in a broad range of discharge scenarios.

  10. Electron cyclotron emission at the fundamental harmonic in GDT magnetic mirror

    Science.gov (United States)

    Shalashov, A. G.; Solomakhin, A. L.; Gospodchikov, E. D.; Lubyako, L. V.; Yakovlev, D. V.; Bagryansky, P. A.

    2017-08-01

    New electron cyclotron emission (ECE) diagnostics has been installed to facilitate the successful experiment of electron cyclotron plasma heating (ECRH) in a large open magnetic trap GDT at Budker Institute. The particularities of ECE in the vicinity of the ECRH frequency were studied experimentally for a broad range of discharge scenarios. The measured thermal emission has partly validated the existing physical conceptions about microwave plasma heating in the machine. Besides the expected emission of thermal electrons, a clearly resolved non-thermal ECE was observed which unambiguously confirmed the presence of suprathermal electrons driven by high-power microwave heating.

  11. Electron cyclotron emission imaging diagnostic system for Rijnhuizen Tokamak Project

    NARCIS (Netherlands)

    Deng, B.H.; Hsia, R. P.; Domier, C.W.; Burns, S. R.; Hillyer, T. R.; N C Luhmann Jr.,; Oyevaar, T.; Donne, A. J. H.; R. T. P. Team,

    1999-01-01

    A 16-channel electron cyclotron emission (ECE) imaging diagnostic system has been developed and installed on the Rijnhuizen Tokamak Project for measuring plasma electron cyclotron emission with a temporal resolution of 2 mu s. The high spatial resolution of the system is achieved by utilizing a low

  12. Characteristics of the fast electron emission produced during the ...

    Indian Academy of Sciences (India)

    of the ionization of surface traps at the expense of the energy which is released in the annihilation ... water adsorption and other characteristics of the fast electron emission produced during the cleavage of crystals. The decay .... Equation (8) shows that for short time duration the rate of fast electron emission should increase ...

  13. Emission of an intense electron beam from a ceramic honeycomb

    Science.gov (United States)

    Friedman, M.; Myers, M.; Hegeler, F.; Swanekamp, S. B.; Sethian, J. D.; Ludeking, L.

    2003-01-01

    Inserting a slab of honeycomb ceramic in front of the emitting surface of a large-area cathode improves the electron beam emission uniformity, decreases the beam current rise and fall times, and maintains a more constant diode impedance. Moreover, changing the cathode material from velvet to carbon fiber achieved a more robust cathode that starts to emit at a higher electric field without a degradation in beam uniformity. In addition, an 80% reduction in the postshot diode pressure was also observed when gamma alumina was deposited on the ceramic. A possible explanation is that reabsorption and recycling of adsorbed gases takes place.

  14. ELECTRON CLOUD OBSERVATIONS AND CURES IN RHIC.

    Energy Technology Data Exchange (ETDEWEB)

    FISCHER,W.; BLASKIEWICZ, M.; HUAN, H.; HSEUH, H.C.; PTITSYN, V.; ROSER, T.; THIEBERGER, P.; TRBOJEVIC, D.; WEI, J.; ZHANG, S.Y.; IRISO, U.

    2007-03-01

    Since 2081 MIC has experienced electron cloud effects, which have limited the beam intensity. These include dynamic pressure rises - including pressure instabilities, tune shifts: electrons, a reduction of the stability threshold for bunches crossing the transition energy, and possibly slow emittance growth. We summarize the main observations in operation and dedicated experiments, as well as countermeasures including baking, NEG coated warm beam pipes, solenoids, bunch patterns, anti-grazing rings, pre-pumped cold beam pipes, and scrubbing.

  15. Carbon adsorption on tungsten and electronic field emission

    Science.gov (United States)

    Márquez-Mijares, Maykel; Lepetit, Bruno; Lemoine, Didier

    2016-03-01

    Electronic emission taking place at the electrodes of high voltage systems and responsible for detrimental breakdown processes is known to be strongly dependent on the cathode surface state and in particular on the presence of carbon contamination. To understand better the effect of carbon adsorption on cathode electronic emission, density functional theory calculations are reported for bulk bcc tungsten as well as for clean and carbon-covered W(100) surfaces for several coverages up to 2 ML. Adsorption geometries and energies, work functions and electronic densities of states are analyzed to assess the effect of the presence of adlayers on surface electronic field emission properties. It is shown that flat carbon adlayer deposition on clean W(100) surfaces induces an increase of the surface work function and a decrease of electronic density near the Fermi level. Both factors contribute to reducing electronic field emission levels.

  16. AKR-like emissions observed by RELEC mission during August-December 2014

    Science.gov (United States)

    Marek, Michał; Matyjasiak, Barbara; Schreiber, Roman; Rothkaehl, Hanna; Przepiórka, Dorota

    2017-04-01

    In this work, observations of AKR-like emissions in the frame of RELEC (Relativistic Electron) mission, in the time period from August to December 2014 are presented. Auroral Kilometric Radiation (AKR) consists of intense electromagnetic emissions generated by energetic electron beams in the Electron Cyclotron Maser process at heights above 2000 km in the auroral region. Typically, AKR emissions are observed during geomagnetically disturbed periods in the frequency range from about 35 to 700 kHz. The exact nature of AKR-like emissions observed in the ionosphere as well as on the ground is still not well understood. Preliminary statistical analysis of AKR-like events observed for different invariant latitudes, magnetic local times and altitudes (in the range of 600-850 km, well below AKR sources lower height limit) will be presented.

  17. Existence of a virtual cathode close to a strongly electron emissive wall in low density plasmas

    Energy Technology Data Exchange (ETDEWEB)

    Tierno, S. P., E-mail: sp.tierno@upm.es; Donoso, J. M.; Domenech-Garret, J. L.; Conde, L. [Department of Applied Physics, E.T.S.I. Aeronáutica y del Espacio. Universidad Politécnica de Madrid, 28040 Madrid (Spain)

    2016-01-15

    The interaction between an electron emissive wall, electrically biased in a plasma, is revisited through a simple fluid model. We search for realistic conditions of the existence of a non-monotonic plasma potential profile with a virtual cathode as it is observed in several experiments. We mainly focus our attention on thermionic emission related to the operation of emissive probes for plasma diagnostics, although most conclusions also apply to other electron emission processes. An extended Bohm criterion is derived involving the ratio between the two different electron densities at the potential minimum and at the background plasma. The model allows a phase-diagram analysis, which confirms the existence of the non-monotonic potential profiles with a virtual cathode. This analysis shows that the formation of the potential well critically depends on the emitted electron current and on the velocity at the sheath edge of cold ions flowing from the bulk plasma. As a consequence, a threshold value of the governing parameter is required, in accordance to the physical nature of the electron emission process. The latter is a threshold wall temperature in the case of thermionic electrons. Experimental evidence supports our numerical calculations of this threshold temperature. Besides this, the potential well becomes deeper with increasing electron emission, retaining a fraction of the released current which limits the extent of the bulk plasma perturbation. This noninvasive property would explain the reliable measurements of plasma potential by using the floating potential method of emissive probes operating in the so-called strong emission regime.

  18. Electron Cloud observation in the LHC

    CERN Document Server

    Rumolo, G; Baglin, V; Bartosik, H; Biancacci, N; Baudrenghien, P; Bregliozzi, G; Chiggiato, P; Claudet, S; De Maria, R; Esteban-Muller, J; Favier, M; Hansen, C; Höfle, W; Jimenez, J M; Kain, V; Lanza, G; Li, K S B; Maury Cuna, G H I; Métral, E; Papotti, G; Pieloni, T; Roncarolo, F; Salvant, B; Shaposhnikova, E N; Steinhagen, R J; Tavian, L J; Valuch, D; Venturini Delsolaro, W; Zimmermann, F; Iriso, U; Dominguez, O; Koukovini-Platia, E; Mounet, N; Zannini, C; Bhat, C M

    2011-01-01

    Operation of LHC with bunch trains at different spacings has revealed the formation of an electron cloud inside the machine. The main observations of electron cloud build up are the pressure rise measured at the vacuum gauges in the warm regions, as well as the increase of the beam screen temperature in the cold regions due to an additional heat load. The effects of the electron cloud were also visible as instability and emittance growth affecting the last bunches of longer trains, which could be improved running with higher chromaticity or larger transverse emittances. A summary of the 2010 and 2011 observations and measurements and a comparison with models will be presented. The efficiency of scrubbing to improve the machine running performance will be briefly discussed.

  19. Observations of exoelectron emission associated with heterogeneous catalysis

    Science.gov (United States)

    Hoenig, S. A.; Utter, M. G.

    1977-01-01

    It is suggested that the exoelectron emission from the catalyst may be used to monitor the rate of oxidation of CO and CH4 over palladium catalysts. Indirect heating of the catalyst and atmospheric pressure have no effect upon this monitoring system. Although the mechanism relating catalysis to exoelectron emission is not clear, it is considered possible that electron emission is triggered by the adsorption-desorption cycle.

  20. Airborne observations reveal elevational gradient in tropical forest isoprene emissions

    Energy Technology Data Exchange (ETDEWEB)

    Gu, Dasa; Guenther, Alex B.; Shilling, John E.; Yu, Haofei; Huang, Maoyi; Zhao, Chun; Yang, Qing; Martin, Scot T.; Artaxo, Paulo; Kim, Saewung; Seco, Roger; Stavrakou, Trissevgeni; Longo, Karla M.; Tóta, Julio; de Souza, Rodrigo Augusto Ferreira; Vega, Oscar; Liu, Ying; Shrivastava, Manish; Alves, Eliane G.; Santos, Fernando C.; Leng, Guoyong; Hu, Zhiyuan

    2017-05-23

    Isoprene dominates global non-methane volatile organic compound emissions, and impacts tropospheric chemistry by influencing oxidants and aerosols. Isoprene emission rates vary over several orders of magnitude for different plants, and characterizing this immense biological chemodiversity is a challenge for estimating isoprene emission from tropical forests. Here we present the isoprene emission estimates from aircraft eddy covariance measurements over the Amazonian forest. We report isoprene emission rates that are three times higher than satellite top-down estimates and 35% higher than model predictions. The results reveal strong correlations between observed isoprene emission rates and terrain elevations, which are confirmed by similar correlations between satellite-derived isoprene emissions and terrain elevations. We propose that the elevational gradient in the Amazonian forest isoprene emission capacity is determined by plant species distributions and can substantially explain isoprene emission variability in tropical forests, and use a model to demonstrate the resulting impacts on regional air quality.

  1. Airborne observations reveal elevational gradient in tropical forest isoprene emissions

    Science.gov (United States)

    Gu, Dasa; Guenther, Alex B.; Shilling, John E.; Yu, Haofei; Huang, Maoyi; Zhao, Chun; Yang, Qing; Martin, Scot T.; Artaxo, Paulo; Kim, Saewung; Seco, Roger; Stavrakou, Trissevgeni; Longo, Karla M.; Tóta, Julio; de Souza, Rodrigo Augusto Ferreira; Vega, Oscar; Liu, Ying; Shrivastava, Manish; Alves, Eliane G.; Santos, Fernando C.; Leng, Guoyong; Hu, Zhiyuan

    2017-05-01

    Isoprene dominates global non-methane volatile organic compound emissions, and impacts tropospheric chemistry by influencing oxidants and aerosols. Isoprene emission rates vary over several orders of magnitude for different plants, and characterizing this immense biological chemodiversity is a challenge for estimating isoprene emission from tropical forests. Here we present the isoprene emission estimates from aircraft eddy covariance measurements over the Amazonian forest. We report isoprene emission rates that are three times higher than satellite top-down estimates and 35% higher than model predictions. The results reveal strong correlations between observed isoprene emission rates and terrain elevations, which are confirmed by similar correlations between satellite-derived isoprene emissions and terrain elevations. We propose that the elevational gradient in the Amazonian forest isoprene emission capacity is determined by plant species distributions and can substantially explain isoprene emission variability in tropical forests, and use a model to demonstrate the resulting impacts on regional air quality.

  2. Modification of the electrostatic sheath by secondary emission of electrons

    Energy Technology Data Exchange (ETDEWEB)

    Hall, L. S.; Bernstein, I.

    1976-10-14

    The potential distribution at the surface of a rectilinear one-dimensional plasma in the presence of wall-emitting secondary electrons is computed as a function of the secondary emission coefficient under a variety of plasma conditions.

  3. Field electron emission from a carbon-covered iridium tip

    Science.gov (United States)

    Bernatskii, D. P.; Pavlov, V. G.

    2017-11-01

    The formation of a carbon coating on an iridium field-emission electron emitter by benzene vapor pyrolysis has been studied. Processes on an emitting tip differ from those studied earlier on flat metal surfaces. The resulting coating either represents a monoatomic graphene film on the flat faces of the emitter or consists of graphene clusters. The field electron emission is localized on the edges and in the corners of a faceted graphite outgrowth. After alkali metals are adsorbed on the carbon coating, emissions from the flat faces anomalously grows and localizes on graphene-coated faces with alkali atoms present on the surface and under the graphene film.

  4. Flow bouncing and electron injection observed by Cluster: FLOW BOUNCING AND ELECTRON INJECTION OBSERVED BY CLUSTER

    National Research Council Canada - National Science Library

    Nakamura, R; Baumjohann, W; Panov, E; Volwerk, M; Birn, J; Artemyev, A; Petrukovich, A. A; Amm, O; Juusola, L; Kubyshkina, M. V; Apatenkov, S; Kronberg, E. A; Daly, P. W; Fillingim, M; Weygand, J. M; Fazakerley, A; Khotyaintsev, Y

    2013-01-01

    ... accompanied by enhanced flux of energetic electrons were observed before the flow bouncing. The sequence of events started with a localized dipolarization front and ended with a large scale (>10RE) dipolarization front accompanied by a major increase in energetic electrons at all spacecraft and immediately followed by flow bouncing. Multiple dipolariz...

  5. Color stable white phosphorescent organic light emitting diodes with red emissive electron transport layer

    Energy Technology Data Exchange (ETDEWEB)

    Wook Kim, Jin; Yoo, Seung Il; Sung Kang, Jin [Department of Green Energy & Semiconductor Engineering, Hoseo University, Asan 336-795 (Korea, Republic of); Eun Lee, Song; Kwan Kim, Young [Department of Information Display, Hongik University, Seoul 121-791 (Korea, Republic of); Hwa Yu, Hyeong; Turak, Ayse [Department of Engineering Physics, McMaster University, Hamilton, Ontario L8S 4L7 (Canada); Young Kim, Woo, E-mail: wykim@hoseo.edu [Department of Green Energy & Semiconductor Engineering, Hoseo University, Asan 336-795 (Korea, Republic of); Department of Engineering Physics, McMaster University, Hamilton, Ontario L8S 4L7 (Canada)

    2015-06-28

    We analyzed the performance of multi-emissive white phosphorescent organic light-emitting diodes (PHOLEDs) in relation to various red emitting sites of hole and electron transport layers (HTL and ETL). The shift of the recombination zone producing stable white emission in PHOLEDs was utilized as luminance was increased with red emission in its electron transport layer. Multi-emissive white PHOLEDs including the red light emitting electron transport layer yielded maximum external quantum efficiency of 17.4% with CIE color coordinates (−0.030, +0.001) shifting only from 1000 to 10 000 cd/m{sup 2}. Additionally, we observed a reduction of energy loss in the white PHOLED via Ir(piq){sub 3} as phosphorescent red dopant in electron transport layer.

  6. Potential applications of electron emission membranes in medicine

    Energy Technology Data Exchange (ETDEWEB)

    Bilevych, Yevgen [Fraunhofer Institute for Reliability and Microintegration (IZM), Berlin (Germany); University of Bonn, Bonn (Germany); Brunner, Stefan E. [Delft University of Technology, Delft (Netherlands); Stefan Meyer Institute for Subatomic Physics, Austrian Academy of Sciences, Vienna (Austria); Chan, Hong Wah; Charbon, Edoardo [Delft University of Technology, Delft (Netherlands); Graaf, Harry van der, E-mail: vdgraaf@nikhef.nl [Delft University of Technology, Delft (Netherlands); Nikhef, Science Park 105, 1098 XG Amsterdam (Netherlands); Hagen, Cornelis W. [Delft University of Technology, Delft (Netherlands); Nützel, Gert; Pinto, Serge D. [Photonis, Roden (Netherlands); Prodanović, Violeta [Delft University of Technology, Delft (Netherlands); Rotman, Daan [Delft University of Technology, Delft (Netherlands); Nikhef, Science Park 105, 1098 XG Amsterdam (Netherlands); University of Amsterdam, Amsterdam (Netherlands); Santagata, Fabio [State Key Lab for Solid State Lighti Changzhou base, F7 R& D HUB 1, Science and Education Town, Changzhou 213161, Jangsu Province (China); Sarro, Lina; Schaart, Dennis R. [Delft University of Technology, Delft (Netherlands); Sinsheimer, John; Smedley, John [Brookhaven National Laboratory, Upton, NY (United States); Tao, Shuxia; Theulings, Anne M.M.G. [Delft University of Technology, Delft (Netherlands); Nikhef, Science Park 105, 1098 XG Amsterdam (Netherlands)

    2016-02-11

    With a miniaturised stack of transmission dynodes, a noise free amplifier is being developed for the detection of single free electrons, with excellent time- and 2D spatial resolution and efficiency. With this generic technology, a new family of detectors for individual elementary particles may become possible. Potential applications of such electron emission membranes in medicine are discussed.

  7. Development of Field-Emission Electron Gun from Carbon Nanotubes

    CERN Document Server

    Hozumi, Y

    2004-01-01

    Aiming to use a narrow energy-spread electron beam easily and low costly on injector electron guns, we have been tested field emission cathodes of carbon nanotubes (CNTs). Experiments for these three years brought us important suggestions and a few rules of thumb. Now at last, anode current of 3.0 [A/cm2

  8. Secondary electron emission in a photocathode rf gun

    Directory of Open Access Journals (Sweden)

    J. H. Han

    2005-03-01

    Full Text Available During the last decades, photocathode rf guns have been proven to be successful for providing very high quality electron beams required for vacuum ultraviolet and x-ray free-electron lasers. Beam dynamics simulations show that the electron beam quality in a rf gun depends strongly on the beam dynamics in the vicinity of the cathode. Therefore, the injection process plays a significant role in the beam performance. Several codes are available to simulate the beam dynamics in the gun. They are able to track the beam under the influence of external fields and space charge forces, but details of the emission processes are still missing in these simulations. In photocathode rf guns, the electron beams have a high charge density. Especially during emission from the cathode, the electrons have a very low velocity and experience high longitudinal space charge forces counteracting the applied accelerating field. Because of the space charge field, some part of the electrons emitted from the cathode might move backward to the cathode where they can produce secondary electrons. A high electric field in the gun cavity, on the other hand, generates a large amount of dark current. If the field-emitted electrons from the cathode or any other surface inside the cavity hit the cathode, secondary electrons can be produced as well. For a detailed understanding of the electron beam and dark current in a rf gun, simulations including a model of the secondary electron emission are necessary. In this paper, a simple model is discussed with an application to the beam dynamics at high emission phases in rf guns. Detailed simulations have been done in comparison to measurements at the Photo Injector Test Facility at DESY in Zeuthen. The primary electrons which are photoemitted from the cathode and the secondary electrons which are produced by the primaries at the cathode could be clearly distinguished in measurements and simulations.

  9. Fast Emission Estimates in China Constrained by Satellite Observations (Invited)

    Science.gov (United States)

    Mijling, B.; van der A, R.

    2013-12-01

    Emission inventories of air pollutants are crucial information for policy makers and form important input data for air quality models. Unfortunately, bottom-up emission inventories, compiled from large quantities of statistical data, are easily outdated for an emerging economy such as China, where rapid economic growth changes emissions accordingly. Alternatively, top-down emission estimates from satellite observations of air constituents have important advantages of being spatial consistent, having high temporal resolution, and enabling emission updates shortly after the satellite data become available. Constraining emissions from concentration measurements is, however, computationally challenging. Within the GlobEmission project of the European Space Agency (ESA) a new algorithm has been developed, specifically designed for fast daily emission estimates of short-lived atmospheric species on a mesoscopic scale (0.25 × 0.25 degree) from satellite observations of column concentrations. The algorithm needs only one forward model run from a chemical transport model to calculate the sensitivity of concentration to emission, using trajectory analysis to account for transport away from the source. By using a Kalman filter in the inverse step, optimal use of the a priori knowledge and the newly observed data is made. We apply the algorithm for NOx emission estimates in East China, using the CHIMERE model together with tropospheric NO2 column retrievals of the OMI and GOME-2 satellite instruments. The observations are used to construct a monthly emission time series, which reveal important emission trends such as the emission reduction measures during the Beijing Olympic Games, and the impact and recovery from the global economic crisis. The algorithm is also able to detect emerging sources (e.g. new power plants) and improve emission information for areas where proxy data are not or badly known (e.g. shipping emissions). The new emission estimates result in a better

  10. Observation of electron-transfer-mediated decay in aqueous solution

    Science.gov (United States)

    Unger, Isaak; Seidel, Robert; Thürmer, Stephan; Pohl, Marvin N.; Aziz, Emad F.; Cederbaum, Lorenz S.; Muchová, Eva; Slavíček, Petr; Winter, Bernd; Kryzhevoi, Nikolai V.

    2017-07-01

    Photoionization is at the heart of X-ray photoelectron spectroscopy (XPS), which gives access to important information on a sample's local chemical environment. Local and non-local electronic decay after photoionization—in which the refilling of core holes results in electron emission from either the initially ionized species or a neighbour, respectively—have been well studied. However, electron-transfer-mediated decay (ETMD), which involves the refilling of a core hole by an electron from a neighbouring species, has not yet been observed in condensed phase. Here we report the experimental observation of ETMD in an aqueous LiCl solution by detecting characteristic secondary low-energy electrons using liquid-microjet soft XPS. Experimental results are interpreted using molecular dynamics and high-level ab initio calculations. We show that both solvent molecules and counterions participate in the ETMD processes, and different ion associations have distinctive spectral fingerprints. Furthermore, ETMD spectra are sensitive to coordination numbers, ion-solvent distances and solvent arrangement.

  11. Observation of emission from xenon hydride molecules

    Science.gov (United States)

    Vlasenko, A. A.; Lakoba, I. S.; Chernov, S. P.; Esselbakh, P. B.

    1986-08-01

    A previously unobserved band with an intensity peak at a wavelength of 190 nm and a halfwidth of 6 nm has been detected in the emission spectra of a plasma produced by a fast repetitively pulsed discharge in a xenon-hydrogen mixture. The present investigation has determined that this band is connected with the penetration of some impurity into the mixture. Specifically, the spectral positions of intensity troughs in the 175-200 nm range are sufficiently close to the wavelengths of the Schumann-Runge bands; hence, it can be assumed that the origin of the troughs is connected with the photoabsorption of molecular oxygen penetrating into the cell through rubber seals. The results are of interest in connection with the development of XeH lasers.

  12. Excimer Emission using 20keV Electron Beam Excitation

    Science.gov (United States)

    Wieser, J.; Ulrich, A.; Murnick, D. E.

    1996-10-01

    A small, continuously emitting rare gas excimer light source has been developed. The gas is excited by a 20keV dc-electron beam. A 300nm thick, 1×1mm^2 SiNx foil sustaining a pressure difference up to 2bar, separates the target volume from the high vacuum part of the electron gun. Spectra of the rare gases Ar, Kr, and Xe have been studied. The monochromator detector system was intensity calibrated in the wavelength range from 115nm to 320nm. Electron beam currents of typically 1μA were used for excitation. When used as a VUV lamp on the second excimer continua, energy conversion efficiencies of 30% were obtained. Emissions originating from the so called left turning points have been clearly observed at 155, 173, and 222nm in Ar_2^*, Kr_2^*, and Xe_2^*, respectively. The so called third continua between 185nm and 240nm (Ar), 220nm and 250nm (Kr), and at 270nm (Xe) have been studied. A new continuum in Xe at 280nm was found. (Funded by the A.v.Humboldt Foundation and NSF (CTS 94-19440). The authors acknowledge support by H. Huggins, A. Liddle and W.L. Brown (Bell Laboratories, Lucent Technologies))

  13. On novel mechanisms of slow ion induced electron emission

    CERN Document Server

    Eder, H

    2000-01-01

    impact of singly and doubly charged ions on poly- and monocrystalline aluminum surfaces were performed. From the results we conclude that direct plasmon excitation by slow ions occurs due to the potential energy of the projectile in a quasi-resonant fashion. The highest relative plasmon intensities were found for impact of 5 keV Ne+ on Al(111) with 5 % of the total yield. For impact of H + and H sub 2 + characteristical differences were observed for Al(111) and polycrystalline aluminum. We show that structures in the spectrum for monocrystalline aluminum arise from diffraction of ejected electrons instead of plasmon excitation as previously assumed. The present work has contributed in new ways to the field of slow ion induced electron emission. First, measurements of the total electron yield gamma for impact of slow singly and multiply charged ions on atomically clean polycrystalline gold and graphite have been made. The respective yields were determined by current measurements and measurements of the electro...

  14. Deterministic Cold Cathode Electron Emission from Carbon Nanofibre Arrays

    Science.gov (United States)

    Cole, Matthew T.; Teo, Kenneth B. K.; Groening, Oliver; Gangloff, Laurent; Legagneux, Pierre; Milne, William I.

    2014-05-01

    The ability to accurately design carbon nanofibre (CN) field emitters with predictable electron emission characteristics will enable their use as electron sources in various applications such as microwave amplifiers, electron microscopy, parallel beam electron lithography and advanced Xray sources. Here, highly uniform CN arrays of controlled diameter, pitch and length were fabricated using plasma enhanced chemical vapour deposition and their individual emission characteristics and field enhancement factors were probed using scanning anode field emission mapping. For a pitch of 10 µm and a CN length of 5 µm, the directly measured enhancement factors of individual CNs was 242, which was in excellent agreement with conventional geometry estimates (240). We show here direct empirical evidence that in regular arrays of vertically aligned CNs the overall enhancement factor is reduced when the pitch between emitters is less than half the emitter height, in accordance to our electrostatic simulations. Individual emitters showed narrow Gaussian-like field enhancement distributions, in excellent agreement with electric field simulations.

  15. Egret observations of the extragalactic gamma-ray emission

    DEFF Research Database (Denmark)

    Sreekumar, P.; Bertsch, D.L.; Dingus, B.L.

    1998-01-01

    . The analysis indicates that the extragalactic emission is well described by a power-law photon spectrum with an index of -(2.10 +/- 0.03) in the 30 MeV to 100 GeV energy range. No large-scale spatial anisotropy or changes in the energy spectrum are observed in the deduced extragalactic emission. The most......The all-sky survey in high-energy gamma rays (E > 30 MeV) carried out by EGRET aboard the Compton Gamma Ray Observatory provides a unique opportunity to examine in detail the diffuse gamma-ray emission. The observed diffuse emission has a Galactic component arising from cosmic-ray interactions...... with the local interstellar gas and radiation, as well as an almost uniformly distributed component that is generally believed to originate outside the Galaxy. Through a careful study and removal of the Galactic diffuse emission, the flux, spectrum, and uniformity of the extragalactic emission are deduced...

  16. Schemes of Superradiant Emission from Electron Beams and "Spin-Flip Emission of Radiation"

    CERN Document Server

    Gover, A

    2005-01-01

    A unified analysis for Superradiant emission from bunched electron beams in various kinds of radiation scheme is presented. Radiation schemes that can be described by the formulation include Pre-bunched FEL (PB-FEL), Coherent Synchrotron Radiation (CSR), Smith-Purcell Radiation, Cerenkov-Radiation, Transition-Radiation and more. The theory is based on mode excitation formulation - either discrete or continuous (the latter - in open structures). The discrete mode formulation permits simple evaluation of the spatially coherent power and spectral power of the source. These figures of merit of the radiation source are useful for characterizing and comparing the performance of different radiation schemes. When the bunched electron beam emits superradiantly, these parameters scale like the square of the number of electrons, orders of magnitude more than spontaneous emission. The formulation applies to emission from single electron bunches, periodically bunched beams, or emission from a finite number of bunches in a...

  17. Surface-electronic-state effects in electron emission from the Be(0001) surface

    Energy Technology Data Exchange (ETDEWEB)

    Archubi, C. D. [Instituto de Astronomia y Fisica del Espacio, casilla de correo 67, sucursal 28, C1428EGA, Buenos Aires (Argentina); Gravielle, M. S. [Instituto de Astronomia y Fisica del Espacio, casilla de correo 67, sucursal 28, C1428EGA, Buenos Aires (Argentina); Departamento de Fisica, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Buenos Aires (Argentina); Silkin, V. M. [Donostia International Physics Center, E-20018 San Sebastian (Spain); Departamento de Fisica de Materiales, Facultad de Ciencias Quimicas, Universidad del Pais Vasco, Apartado 1072, E-20080 San Sebastian (Spain); IKERBASQUE, Basque Foundation for Science, E-48011 Bilbao (Spain)

    2011-07-15

    We study the electron emission produced by swift protons impinging grazingly on a Be(0001) surface. The process is described within a collisional formalism using the band-structure-based (BSB) approximation to represent the electron-surface interaction. The BSB model provides an accurate description of the electronic band structure of the solid and the surface-induced potential. Within this approach we derive both bulk and surface electronic states, with these latter characterized by a strong localization at the crystal surface. We found that such surface electronic states play an important role in double-differential energy- and angle-resolved electron emission probabilities, producing noticeable structures in the electron emission spectra.

  18. Upper Limits on O VI Emission from Voyager Observations

    Indian Academy of Sciences (India)

    We have examined 426 Voyager fields distributed across the sky for O VI ( 1032/1038 Å) emission from the Galactic diffuse interstellar medium. No such emission was detected in any of our observed fields. Our most constraining limit was a 90% confidence upper limit of 2600 photons cm-2 sr-1 s-1 on the doublet ...

  19. PLASMA EMISSION BY COUNTER-STREAMING ELECTRON BEAMS

    Energy Technology Data Exchange (ETDEWEB)

    Ziebell, L. F.; Petruzzellis, L. T.; Gaelzer, R. [Instituto de Física, UFRGS, Porto Alegre, RS (Brazil); Yoon, P. H. [Institute for Physical Science and Technology, University of Maryland, College Park, MD (United States); Pavan, J., E-mail: luiz.ziebell@ufrgs.br, E-mail: yoonp@umd.edu, E-mail: joel.pavan@ufpel.edu.br [Instituto de Física e Matemática, UFPel, Pelotas, RS (Brazil)

    2016-02-10

    The radiation emission mechanism responsible for both type-II and type-III solar radio bursts is commonly accepted as plasma emission. Recently Ganse et al. suggested that type-II radio bursts may be enhanced when the electron foreshock geometry of a coronal mass ejection contains a double hump structure. They reasoned that the counter-streaming electron beams that exist between the double shocks may enhance the nonlinear coalescence interaction, thereby giving rise to more efficient generation of radiation. Ganse et al. employed a particle-in-cell simulation to study such a scenario. The present paper revisits the same problem with EM weak turbulence theory, and show that the fundamental (F) emission is not greatly affected by the presence of counter-streaming beams, but the harmonic (H) emission becomes somewhat more effective when the two beams are present. The present finding is thus complementary to the work by Ganse et al.

  20. Field electron emission from dense array of microneedles of tungsten

    Energy Technology Data Exchange (ETDEWEB)

    Okuyama, F.; Aoyagi, M.; Kitai, T.; Ishikawa, K.

    1978-01-01

    Characteristics of field electron emission from the dense array of microneedles of tungsten prepared on a 10-..mu..m tungsten filament were measured at an environmental pressure of approx.1 x 10/sup -8/ Torr (1.33 x 10/sup -6/ Pa). Electron emission was not uniform over the filament surface, but the variation of emission current with applied voltage explicitly obeyed the Fowler-Nordheim relationship. At an emission current of approx.10/sup -4/ A, a vacuum arc was induced that led to a permanent change in current-voltage characteristic. Current fluctuation was dependent on emitter temperature and applied voltage, and the lowest fluctuation of about 4% was routinely obtained at approx.550 K and at applied voltages several percent lower than the arc-inducing voltage. Macroscopic current density amounted to approx.20-80 mA/cm/sup 2/ at the best stability.

  1. Locally Resolved Electron Emission Area and Unified View of Field Emission from Ultrananocrystalline Diamond Films

    Energy Technology Data Exchange (ETDEWEB)

    Chubenko, Oksana [Department of Physics, The George Washington University, 725 21st Street NW, Washington, D.C. 20052, United States; Euclid TechLabs, 365 Remington Boulevard, Bolingbrook, Illinois 60440, United States; Baturin, Stanislav S. [PSD Enrico; Kovi, Kiran K. [Euclid TechLabs, 365 Remington Boulevard, Bolingbrook, Illinois 60440, United States; Sumant, Anirudha V. [Center for Nanoscale Materials, Argonne National Laboratory, 9700 S. Cass Avenue, Argonne, Illinois 60439, United States; Baryshev, Sergey V. [Euclid TechLabs, 365 Remington Boulevard, Bolingbrook, Illinois 60440, United States

    2017-09-13

    One of the common problems in case of field emission from polycrystalline diamond films, which typically have uniform surface morphology, is uncertainty in determining exact location of electron emission sites across the surface. Although several studies have suggested that grain boundaries are the main electron emission source, it is not particularly clear what makes some sites emit more than the others. It is also practically unclear how one could quantify the actual electron emission area and therefore field emission current per unit area. In this paper we study the effect of actual, locally resolved, field emission (FE) area on electron emission characteristics of uniform planar highly conductive nitrogen-incorporated ultrananocrystalline diamond ((N)UNCD) field emitters. It was routinely found that field emission from as-grown planar (N)UNCD films is always confined to a counted number of discrete emitting centers across the surface which varied in size and electron emissivity. It was established that the actual FE area critically depends on the applied electric field, as well as that the actual FE area and the overall electron emissivity improve with sp2 fraction present in the film irrespectively of the original substrate roughness and morphology. To quantify the actual FE area and its dependence on the applied electric field, imaging experiments were carried out in a vacuum system in a parallel-plate configuration with a specialty anode phosphor screen. Electron emission micrographs were taken concurrently with I-V characteristics measurements. In addition, a novel automated image processing algorithm was developed to process extensive imaging datasets and calculate emission area per image. By doing so, it was determined that the emitting area was always significantly smaller than the FE cathode surface area. Namely, the actual FE area would change from 5×10-3 % to 1.5 % of the total cathode area with the applied electric field increased. Finally and most

  2. Probabilistic Model for the Simulation of Secondary Electron Emission

    Energy Technology Data Exchange (ETDEWEB)

    Furman, M

    2004-05-17

    We provide a detailed description of a model and its computational algorithm for the secondary electron emission process. The model is based on a broad phenomenological fit to data for the secondary emission yield (SEY) and the emitted-energy spectrum. We provide two sets of values for the parameters by fitting our model to two particular data sets, one for copper and the other one for stainless steel.

  3. The Zodiacal Emission Observations with the AKARI Infrared Camera

    Science.gov (United States)

    Pyo, J.; Ueno, M.; Kwon, S. M.; Hong, S. S.; Ishihara, D.; Ishiguro, M.; Usui, F.; Matsumoto, T.; Jeong, W.-S.; Ootsubo, T.; Matsuura, S.; Mukai, T.

    2012-05-01

    From the pointed and scanning observations of the AKARI at the mid-infrared wavelengths, we retrieved the fine-, small-, and global-scale properties of the zodiacal emission and the interplanetary dust cloud.

  4. Differential electron-Cu{sup 5+} elastic scattering cross sections extracted from electron emission in ion-atom collisions

    Energy Technology Data Exchange (ETDEWEB)

    Liao, C.; Hagmann, S.; Bhalla, C.P.; Grabbe, S.R.; Cocke, C.L.; Richard, P. [J. R. Macdonald Laboratory, Kansas State University, Manhattan, Kansas 66506 (United States); Liao, C. [Jet Propulsion Laboratory, California Institute of Technology, Pasadena, California 91109 (United States)

    1999-04-01

    We present a method of deriving energy and angle-dependent electron-ion elastic scattering cross sections from doubly differential cross sections for electron emission in ion-atom collisions. By analyzing the laboratory frame binary encounter electron production cross sections in energetic ion-atom collisions, we derive projectile frame differential cross sections for electrons elastically scattered from highly charged projectile ions in the range between 60{degree} and 180{degree}. The elastic scattering cross sections are observed to deviate strongly from the Rutherford cross sections for electron scattering from bare nuclei. They exhibit strong Ramsauer-Townsend electron diffraction in the angular distribution of elastically scattered electrons, providing evidence for the strong role of screening played in the collision. Experimental data are compared with partial-wave calculations using the Hartree-Fock model. {copyright} {ital 1999} {ital The American Physical Society}

  5. Particulate electron beam weld emission hazards in space

    Science.gov (United States)

    Bunton, Patrick H.

    1996-01-01

    The electron-beam welding process is well adapted to function in the environment of space. The Soviets were the first to demonstrate welding in space in the mid-1980's. Under the auspices of the International Space Welding Experiment (ISWE), an on-orbit test of a Ukrainian designed electron-beam welder (the Universal Hand Tool or 'UHT') is scheduled for October of 1997. The potential for sustained presence in space with the development of the international space station raises the possibility of the need for construction and repair in space. While welding is not scheduled to be used in the assembly of the space station, repair of damage from orbiting debris or meteorites is a potential need. Furthermore, safe and successful welding in the space environment may open new avenues for design and construction. The safety issue has been raised with regard to hot particle emissions (spatter) sometimes observed from the weld during operations. On earth the hot particles pose no particular hazard, but in space there exists the possibility for burn-through of the space suit which could be potentially lethal. Contamination of the payload bay by emitted particles could also be a problem.

  6. Contribution of Metal Layer Thickness for Quantitative Backscattered Electron Imaging of Field Emission Scanning Electron Microscopy

    National Research Council Canada - National Science Library

    Kim, Hyonchol; Takei, Hiroyuki; Negishi, Tsutomu; Kudo, Masato; Terazono, Hideyuki; Yasuda, Kenji

    2012-01-01

    ...) imaging in field emission scanning electron microscopy (FE-SEM) were studied to evaluate the potential of using these particles as simultaneously distinguishable labels of target molecules in FE-SEM studies...

  7. Incident ion charge state dependence of electron emission during slow multicharged ion-surface interactions

    Energy Technology Data Exchange (ETDEWEB)

    Hughes, I.G. (Oak Ridge National Laboratory, Oak Ridge, TN 37831-6372 (United States) Joint Institute for Heavy Ion Research, Holifield Heavy Ion Research, Facility, Oak Ridge, TN 37831-6734 (United States)); Havener, C.C.; Overbury, S.H.; Robinson, M.T.; Zehner, D.M. (Oak Ridge National Laboratory, Oak Ridge, TN 37831-6732 (United States)); Zeijlmans van Emmichoven, P.A. (Oak Ridge National Laboratory, Oak Ridge, TN 37831-6732 (United States) Joint Institute for Heavy Ion Research, Holifield Heavy Ion Research Facility, Oak Ridge, TN 37821-6734 (United States)); Meyer, F.W. (Oak Ridge National Laboratory, Oak Ridge, TN 37831-6732 (United States))

    1993-06-05

    Characteristic variations in the total electron yield [gamma] as a function of crystal azimuthal orientation are reported for slow N[sup 2+], N[sup 5+] and N[sup 6+] ions incident on a Au(011) single crystal, together with measurements of [gamma] as a function of incident ion velocity. Kinetic electron emission is shown to arise predominantly in close collisions between incident ions and target atoms, and potential electron emission is found to be essentially constant within our present velocity range. The incident ion charge state is shown to play no role in kinetic electron emission. Extremely fast neutralization times of the order of 10[sup [minus]15] secs are needed to explain the observations.

  8. Electronic field emission models beyond the Fowler-Nordheim one

    Science.gov (United States)

    Lepetit, Bruno

    2017-12-01

    We propose several quantum mechanical models to describe electronic field emission from first principles. These models allow us to correlate quantitatively the electronic emission current with the electrode surface details at the atomic scale. They all rely on electronic potential energy surfaces obtained from three dimensional density functional theory calculations. They differ by the various quantum mechanical methods (exact or perturbative, time dependent or time independent), which are used to describe tunneling through the electronic potential energy barrier. Comparison of these models between them and with the standard Fowler-Nordheim one in the context of one dimensional tunneling allows us to assess the impact on the accuracy of the computed current of the approximations made in each model. Among these methods, the time dependent perturbative one provides a well-balanced trade-off between accuracy and computational cost.

  9. Nonlinear electron emission in ultrashort laser pulses and rescattering suppression

    Science.gov (United States)

    Mikhin, E. A.; Preobrazhenskii, M. A.; Golovinski, P. A.

    2017-11-01

    The process of nonlinear electron emission from a metal surface under the action of femtosecond laser pulse with moderate intensity ~1011 W/cm2 is considered. One-dimensional model is formulated, taking into account the advantage of the p-polarized light in the nonlinear emission. The time dependent Schrödinger equation with fixed equilibrium boundary conditions is solved in the half-space using the Laplace transform technique. The energy spectrum of emitted electrons is presented, including analysis of dependence on the laser pulse parameters. In the framework of classical mechanics, the impact of additional dc electric field on the rescattering of emitted electron on the metal surface is investigated. The model reproduces the fiches of electron energy distribution and can be used at arbitrary Keldysh parameters.

  10. A Statistical Model for Determining the Probability of Observing Exoplanetary Radio Emissions

    Science.gov (United States)

    Garcia, R.; Knapp, M.; Winterhalter, D.; Majid, W.

    2015-12-01

    The idea that extrasolar planets should emit radiation in the low-frequency radio regime is a generalization of the observation of decametric and kilometric radio emissions from magnetic planets in our own solar system, yet none of these emissions have been observed. Such radio emissions are a result of the interactions between the host star's magnetized wind and the planet's magnetosphere that accelerate electrons along the field lines, which leads to radio emissions at the electron gyrofrequency. To understand why these emissions had not yet been observed, and to guide in target selection for future detection efforts, we took a statistical approach to determine what the ideal location in parameter space was for these hypothesized exoplanetary radio emissions to be detected. We derived probability distribution functions from current datasets for the observably constrained parameters (such as the radius of the host star), and conducted a review of the literature to construct reasonable probability distribution functions to obtain the unconstrained parameters (such as the magnetic field strength of the exoplanet). We then used Monte Carlo sampling to develop a synthetic population of exoplanetary systems and calculated whether the radio emissions from the systems were detectable depending on the angle of beaming, frequency (above the ionospheric cutoff rate of 10 MHz) and flux density (above 5 mJy) of the emission. From millions of simulations we derived a probability distribution function in parameter space as a function of host star type, orbital radius and planetary or host star radius. The probability distribution function illustrated the optimal parameter values of an exoplanetary system that may make the system's radio emissions detectable to current and currently under development instruments such as the SKA. We found that detection of exoplanetary radio emissions favor planets larger than 5 Earth radii and within 1 AU of their M dwarf host.

  11. A tiered observational system for anthropogenic methane emissions

    Science.gov (United States)

    Duren, R. M.; Miller, C. E.; Hulley, G. C.; Hook, S. J.; Sander, S. P.

    2014-12-01

    Improved understanding of anthropogenic methane emissions is required for closing the global carbon budget and addressing priority challenges in climate policy. Several decades of top-down and bottom-up studies show that anthropogenic methane emissions are systematically underestimated in key regions and economic sectors. These uncertainties have been compounded by the dramatic rise of disruptive technologies (e.g., the transformation in the US energy system due to unconventional gas and oil production). Methane flux estimates derived from inverse analyses and aircraft-based mass balance approaches underscore the disagreement in nationally and regionally reported methane emissions as well as the possibility of a long-tail distribution in fugitive emissions spanning the US natural gas supply chain; i.e. a small number of super-emitters may be responsible for most of the observed anomalies. Other studies highlight the challenges of sectoral and spatial attribution of fugitive emissions - including the relative contributions of dairies vs oil and gas production or disentangling the contributions of natural gas transmission, distribution, and consumption or landfill emissions in complex urban environments. Limited observational data remains a foundational barrier to resolving these challenges. We present a tiered observing system strategy for persistent, high-frequency monitoring over large areas to provide remote detection, geolocation and quantification of significant anthropogenic methane emissions across cities, states, basins and continents. We describe how this would both improve confidence in methane emission estimates and expedite resolution of fugitive emissions and leaks. We summarize recent prototype field campaigns that employ multiple vantage points and measurement techniques (including NASA's CARVE and HyTES aircraft and PanFTS instrument on Mt Wilson). We share preliminary results of this tiered observational approach including examples of individual

  12. Electron-bombarded 〈110〉-oriented tungsten tips for stable tunneling electron emission

    Energy Technology Data Exchange (ETDEWEB)

    Yamada, T. K.; Abe, T.; Nazriq, N. M. K.; Irisawa, T. [Graduate School of Advanced Integration Science, Chiba University, 1-33 Yayoi-cho, Inage-ku, Chiba 263-8522 (Japan)

    2016-03-15

    A clean tungsten (W) tip apex with a robust atomic plane is required for producing a stable tunneling electron emission under strong electric fields. Because a tip apex fabricated from a wire by aqueous chemical etching is covered by impurity layers, heating treatment in ultra-high vacuum is experimentally known to be necessary. However, strong heating frequently melts the tip apex and causes unstable electron emissions. We investigated quantitatively the tip apex and found a useful method to prepare a tip with stable tunneling electron emissions by controlling electron-bombardment heating power. Careful characterizations of the tip structures were performed with combinations of using field emission I–V curves, scanning electron microscopy, X-ray diffraction (transmitted Debye-Scherrer and Laue) with micro-parabola capillary, field ion microscopy, and field emission microscopy. Tips were chemically etched from (1) polycrystalline W wires (grain size ∼1000 nm) and (2) long-time heated W wires (grain size larger than 1 mm). Heating by 10-40 W (10 s) was found to be good enough to remove oxide layers and produced stable electron emission; however, around 60 W (10 s) heating was threshold power to increase the tip radius, typically +10 ± 5 nm (onset of melting). Further, the grain size of ∼1000 nm was necessary to obtain a conical shape tip apex.

  13. Quantum interferences induced by multiple scattering paths of the electron prior to emission in large molecules

    Science.gov (United States)

    Agueny, H.; Makhoute, A.; Tökési, K.; Dubois, A.; Hansen, J. P.

    2017-09-01

    We theoretically investigate electron emission process from a dimer generated by swift highly charged ions. The process under consideration is dealt with a non-perturbative approach by solving the time-dependent Schrödinger equation on a two-dimensional spatial grid. Numerical calculations show rich structures related to the multiple scattering paths of the electron prior to emission. This manifests by the emergence of additional oscillations with high-frequency superimposed on the Young-type oscillatory structure in the observed electron-ejected spectrum. This is not the case when calculations are performed based on the superposition principle, in which the final wave function is just a coherent sum of component wave functions described the electron emission from two-independent atoms. Within this assumption, only a direct electron emission process is taken into account. We find that contributions arising from these multiple scattering paths modify the dynamic electron emission process, and therefore, show the incorrect applicability of the above-mentioned principle, in concordance with the recent findings based on a simple three-slit interference experiment, reported in Sawant et al. (2014).

  14. Radiation emission from braided electrons in interacting wakefields

    Science.gov (United States)

    Wallin, Erik; Gonoskov, Arkady; Marklund, Mattias

    2017-09-01

    The radiation emission from electrons wiggling in a laser wakefield acceleration (LWFA) process, being initially considered as a parasitic effect for the electron energy gain, can eventually serve as a novel X-ray source, which could be used for diagnostic purposes. Although several schemes for enhancing the X-ray emission in LWFA has been recently proposed and analyzed, finding an efficient way to use and control this radiation emission remains an important problem. Based on analytical estimates and 3D particle-in-cell simulations, we here propose and examine a new method utilizing two colliding LWFA patterns with an angle in between their propagation directions. Varying the angle of collision, the distance of acceleration before the collision and other parameters provide an unprecedented control over the emission parameters. Moreover, we reveal here that for a collision angle of 5°, the two wakefields merge into a single LWFA cavity, inducing strong and stable collective oscillations between the two trapped electron bunches. This results in an X-ray emission which is strongly peaked, both in the spatial and frequency domains. The basic concept of the proposed scheme may pave a way for using LWFA radiation sources in many important applications, such as phase-contrast radiography.

  15. Electron field emission from sp 2-induced insulating to metallic ...

    Indian Academy of Sciences (India)

    Home; Journals; Bulletin of Materials Science; Volume 33; Issue 3. Electron field emission from 2-induced insulating to metallic behaviour of amorphous carbon (-C) films. Pitamber Mahanandia P N Viswakarma Prasad Vishnu Bhotla S V Subramanyam Karuna Kar Nanda. Thin Films and Nanomatter Volume 33 Issue 3 ...

  16. GOSAT observations of anthropogenic emission of carbon dioxide and methane

    Science.gov (United States)

    Janardanan, Rajesh; Maksyutov, Shamil; Oda, Tomohiro; Saito, Makoto; Ito, Akihiko; Kaiser, Johannes W.; Ganshin, Alexander; Yoshida, Yukio; Yokota, Tatsuya; Matsunaga, Tsuneo

    2017-04-01

    Carbon dioxide (CO2) and methane (CH4) are the most important greenhouse gases in terms of radiative forcing. Human activities such as combustion of fossil fuel (for CO2), and gas leakage, animal agriculture, rice cultivation and landfill emissions (for CH4), are considered to be major sources of their emissions. Global emissions datasets usually depend on emission estimates reported by countries, which are seldom evaluated in an objective way. Here we present a method for delineating anthropogenic contributions to global atmospheric CO2 and CH4 (2009-2014) concentration fields using GOSAT observations of column-average dry air mole fractions (XCO2 and XCH4) and atmospheric transport model simulations using high-resolution emissions datasets (ODIAC for CO2 and EDGAR for CH4). The XCO2 and XCH4 concentration enhancements due to anthropogenic emissions are estimated at all GOSAT observation locations using the transport model simulation. We calculated threshold values to classify GOSAT observations into two categories: (1) data influenced by the anthropogenic sources and (2) those not influenced. We defined a clean background (averaged concentrations of GOSAT data that are free from contamination) in 10˚ ×10˚ regions over the globe and subtracted the background values from individual GOSAT observations. The anomalies (GOSAT observed values minus background values) were binned and compared to model-based anomalies over continental regions and selected countries. For CO2, we have found global and regional linear relationships between model and observed anomalies especially for Eurasia and North America. The analysis for East Asian region showed a systematic bias that is somewhat comparable in magnitude to the uncertainties in emission inventories in that region, which were reported by recent studies. In the case of CH4, we found a good match between inventory-based estimates and GOSAT observations for continental regions and large countries. The inventory

  17. Partial localization in coherent electron emission from asymmetric diatomic molecules

    Energy Technology Data Exchange (ETDEWEB)

    Tachino, C A; Galassi, M E; Rivarola, R D [Instituto de FIsica Rosario, Consejo Nacional de Investigaciones CientIficas y Tecnicas - Universidad Nacional de Rosario, Av. Pellegrini 250, 2000 Rosario (Argentina); MartIn, F, E-mail: rivarola@fceia.unr.edu.a [Departamento de QuImica, Modulo 13, Universidad Autonoma de Madrid, 28049 Madrid (Spain)

    2010-07-14

    The presence of interference patterns in doubly differential cross sections is investigated for single electron ionization of a heteronuclear system, the HeH{sup +} molecular ion, produced by highly energetic protons. These interferences, which are due to coherent electron emission from the vicinity of the target nuclei, are preserved even after averaging over all molecular orientations. However, when compared with the homonuclear H{sub 2} target case, the effect appears to be less pronounced due to the partial localization of the target electrons around the alpha particle centre. Similarities and differences with the case of photon beams are also discussed.

  18. Transport Theory for Kinetic Emission of Secondary Electrons from Solids

    DEFF Research Database (Denmark)

    Schou, Jørgen

    1980-01-01

    . These quantities are determined from the solutions to a system of Boltzmann transport equations. Input quantities are the cross sections for collisions between the involved particles and the surface barrier of the target. A general power cross section has been utilized in the analytical procedure. It is shown......Kinetic secondary electron emission from a solid target resulting from incidence of keV electrons or keV and MeV ions is treated theoretically on the basis of ionization cascade theory. The energy and angular distribution and the yield of secondary electrons are calculated for a random target...

  19. Electron cyclotron emission measurements on JET: Michelson interferometer, new absolute calibration, and determination of electron temperature

    NARCIS (Netherlands)

    Schmuck, S.; Fessey, J.; Gerbaud, T.; Alper, B.; Beurskens, M. N. A.; de la Luna, E.; Sirinelli, A.; Zerbini, M.

    2012-01-01

    At the fusion experiment JET, a Michelson interferometer is used to measure the spectrum of the electron cyclotron emission in the spectral range 70-500 GHz. The interferometer is absolutely calibrated using the hot/cold technique and, in consequence, the spatial profile of the plasma electron

  20. Solar flare impulsive phase emission observed with SDO/EVE

    Energy Technology Data Exchange (ETDEWEB)

    Kennedy, Michael B.; Milligan, Ryan O.; Mathioudakis, Mihalis; Keenan, Francis P., E-mail: mkennedy29@qub.ac.uk [Astrophysics Research Centre, School of Mathematics and Physics, Queen' s University Belfast, University Road, Belfast BT7 1NN (United Kingdom)

    2013-12-10

    Differential emission measures (DEMs) during the impulsive phase of solar flares were constructed using observations from the EUV Variability Experiment (EVE) and the Markov-Chain Monte Carlo method. Emission lines from ions formed over the temperature range log T{sub e} = 5.8-7.2 allow the evolution of the DEM to be studied over a wide temperature range at 10 s cadence. The technique was applied to several M- and X-class flares, where impulsive phase EUV emission is observable in the disk-integrated EVE spectra from emission lines formed up to 3-4 MK and we use spatially unresolved EVE observations to infer the thermal structure of the emitting region. For the nine events studied, the DEMs exhibited a two-component distribution during the impulsive phase, a low-temperature component with peak temperature of 1-2 MK, and a broad high-temperature component from 7 to 30 MK. A bimodal high-temperature component is also found for several events, with peaks at 8 and 25 MK during the impulsive phase. The origin of the emission was verified using Atmospheric Imaging Assembly images to be the flare ribbons and footpoints, indicating that the constructed DEMs represent the spatially average thermal structure of the chromospheric flare emission during the impulsive phase.

  1. Emissions of Toxic Carbonyls in an Electronic Cigarette

    Directory of Open Access Journals (Sweden)

    Guthery William

    2016-01-01

    Full Text Available Electronic cigarettes (e-cigs provide a smoke-free alternative for inhalation of nicotine without the vast array of toxic and carcinogenic combustion products produced by tobacco smoke. Elevated levels of toxic carbonyls may be generated during vaporisation; however, it is unclear whether that is indicative of a fault with the device or is due to the applied conditions of the test. A device, designed and built at this facility, was tested to determine the levels of selected toxic carbonyls. The reservoir was filled with approximately 960 mg of an e-liquid formulation containing 1.8% (w/v nicotine. Devices were puffed 200 times in blocks of 40 using a standardised regime consisting of a 55 mL puff volume; 3 s puff duration; 30 s puff interval; square wave puff profile. Confirmatory testing for nicotine and total aerosol delivery resulted in mean (n = 8 values of 10 mg (RSD 12.3% and 716 mg (RSD 11.2%, respectively. Emissions of toxic carbonyls were highly variable yet were between < 0.1% and 22.9% of expected levels from a Kentucky Reference Cigarette (K3R4F puffed 200 times under Health Canada Intense smoking conditions. It has been shown that a device built to a high specification with relatively consistent nicotine and aerosol delivery emits inconsistent levels of carbonyls. The exposure is greatly reduced when compared with lit tobacco products. However, it was observed that as the reservoirs neared depletion then emission levels were significantly higher

  2. Electron cyclotron emission imaging diagnostic system for Rijnhuizen Tokamak Project

    Energy Technology Data Exchange (ETDEWEB)

    Deng, B.H.; Hsia, R.P.; Domier, C.W.; Burns, S.R.; Hillyer, T.R.; Luhmann, N.C. Jr. [University of California at Davis, 228 Walker Hall, Davis, California 95616 (United States); Oyevaar, T.; Donne, A.J. [FOM-Inst. voor Plasmafysica Rijnhuizen, Association Euratom-FOM (International organizations without location); RTP team

    1999-01-01

    A 16-channel electron cyclotron emission (ECE) imaging diagnostic system has been developed and installed on the Rijnhuizen Tokamak Project for measuring plasma electron cyclotron emission with a temporal resolution of 2 {mu}s. The high spatial resolution of the system is achieved by utilizing a low cost linear mixer/receiver array. Unlike conventional ECE diagnostics, the sample volumes of the ECE imaging system are aligned vertically, and can be shifted across the plasma cross-section by varying the local oscillator frequency, making possible 2D measurements of electron temperature profiles and fluctuations. The poloidal/radial wavenumber spectra and correlation lengths of T{sub e} fluctuations in the plasma core can also be obtained by properly positioning the focal plane of the imaging system. Due to these unique features, ECE imaging is an ideal tool for plasma transport study. Technical details of the system are described, together with preliminary experimental results. {copyright} {ital 1999 American Institute of Physics.}

  3. Relativistic quantum dynamics in strong fields: Photon emission from heavy, few-electron ions

    Energy Technology Data Exchange (ETDEWEB)

    Fritzsche, S. [Kassel Univ. (Germany). Inst. fuer Physik; Indelicato, P. [Lab. Kastler Brossel, Ecole Normale Superieure et Universite Pierre et Marie Curie, Paris (France); Stoehlker, T. [Frankfurt Univ. (Germany). Inst. fuer Kernphysik

    2005-03-01

    Recent progress in the study of the photon emission from highly-charged heavy ions is reviewed. These investigations show that high-Z ions provide a unique tool for improving the understanding of the electron-electron and electron-photon interaction in the presence of strong fields. Apart from the bound-state transitions, which are accurately described in the framework of quantum electrodynamics, much information has been obtained also from the radiative capture of (quasi-) free electrons by high-Z ions. Many features in the observed spectra hereby confirm the inherently relativistic behavior of even the simplest compound quantum systems in nature. (orig.)

  4. Electron Correlations Observed through Intensity Interferometry

    Energy Technology Data Exchange (ETDEWEB)

    Schulz, M. [Universitaet Freiburg, Fakultaet fuer Physik, D-79104 Freiburg, (Germany); Physics Department and Laboratory for Atomic, Molecular and Optical Research, University of Missouri-Rolla, Rolla, Missouri 65409 (United States); Moshammer, R. [Universitaet Freiburg, Fakultaet fuer Physik, D-79104 Freiburg, (Germany); Schmitt, W. [Universitaet Freiburg, Fakultaet fuer Physik, D-79104 Freiburg, (Germany); Kollmus, H. [Universitaet Freiburg, Fakultaet fuer Physik, D-79104 Freiburg, (Germany); Feuerstein, B. [Universitaet Freiburg, Fakultaet fuer Physik, D-79104 Freiburg, (Germany); Mann, R. [Gesellschaft fuer Schwerionenforschung, D-64291 Darmstadt, (Germany); Hagmann, S. [Department of Physics, Kansas State University, Manhattan, Kansas 66506-2601 (United States); Ullrich, J. [Universitaet Freiburg, Fakultaet fuer Physik, D-79104 Freiburg, (Germany)

    2000-01-31

    Intensity interferometry was applied to study electron correlations in doubly ionizing ion-atom collisions. In this method, the probability to find two electrons emitted in the same double ionization event with a certain momentum difference is compared to the corresponding probability for two uncorrelated electrons from two independent events. The ratio of both probabilities, the so-called correlation function, is found to sensitively reveal electron correlation effects, but it is rather insensitive to the collision dynamics. (c) 2000 The American Physical Society.

  5. Field-induced electron emission from nanoporous carbon of various types

    Directory of Open Access Journals (Sweden)

    Alexander V. Arkhipov

    2015-03-01

    Full Text Available The influence of fabrication technology on field electron emission properties of nanoporous carbon (NPC has been investigated. Samples of NPC derived from different carbides via chlorination at different temperatures demonstrated similar low-field emission ability with the threshold electric field strength of 2–3 V/μm. This property correlated with the presence of nanopores with the characteristic size of 0.5–1.2 nm determining high values of specific surface area (more than 800 m2/g of the material. In most cases, voltage–current characteristics of emission were approximately linear in Fowler–Nordheim (FN coordinates (excluding the low-current part near the emission threshold, but the plot slope angles were in notable disagreement with the known material morphology and electronic properties, and this could not be explained within the frames of FN emission theory. We suggest that the actual emission mechanism for NPC involves hot electrons generated at internal boundaries, and that emission centers may be associated with relatively large (20–100 nm onion-like particles observed in many microscopy images.

  6. System of video observation for electron beam welding process

    Science.gov (United States)

    Laptenok, V. D.; Seregin, Y. N.; Bocharov, A. N.; Murygin, A. V.; Tynchenko, V. S.

    2016-04-01

    Equipment of video observation system for electron beam welding process was developed. Construction of video observation system allows to reduce negative effects on video camera during the process of electron beam welding and get qualitative images of this process.

  7. Ultrafast electron field emission from gold resonant antennas studied by two terahertz pulse experiments

    DEFF Research Database (Denmark)

    Iwaszczuk, Krzysztof; Zalkovskij, Maksim; Strikwerda, Andrew C.

    2015-01-01

    Summary form only given. Ultrafast electron field emission from gold resonant antennas induced by strong terahertz (THz) transient is investigated using two THz pulse experiments. It is shown that UV emission from nitrogen plasma generated by liberated electrons is a good indication of the local...... electric field at the antenna tip. Using this method resonant properties of antennas fabricated on high resistivity silicon are investigated in the strong field regime. Decrease of antenna Q-factor due to ultrafast carrier multiplication in the substrate is observed....

  8. SCIAMACHY formaldehyde observations: constraint for isoprene emission estimates over Europe?

    Directory of Open Access Journals (Sweden)

    G. Dufour

    2009-03-01

    Full Text Available Formaldehyde (HCHO is an important intermediate compound in the degradation of volatile organic compounds (VOCs in the troposphere. Sources of HCHO are largely dominated by its secondary production from VOC oxidation, methane and isoprene being the main precursors in unpolluted areas. As a result of the moderate lifetime of HCHO, its spatial distribution is determined by reactive hydrocarbon emissions. We focus here on Europe and investigate the influence of the different emissions on HCHO tropospheric columns with the CHIMERE chemical transport model in order to interpret the comparisons between SCIAMACHY and simulated HCHO columns. Europe was never specifically studied before for these purposes using satellite observations. The bias between measurements and model is less than 20% on average. The differences are discussed according to the errors on the model and the observations and remaining discrepancies are attributed to a misrepresentation of biogenic emissions. This study requires the characterisation of: (1 the model errors and performances concerning formaldehyde. The errors on the HCHO columns, mainly related to chemistry and mixed emission types, are evaluated to 2×1015 molecule/cm2 and the model performances evaluated using surface measurements are satisfactory (~13%; (2 the observation errors that define the needs in spatial and temporal averaging for meaningful comparisons. Using SCIAMACHY observations as constraint for biogenic isoprene emissions in an inverse modelling scheme reduces their uncertainties by about a factor of two in region of intense emissions. The retrieved correction factors for the isoprene emissions range from a factor of 0.15 (North Africa to a factor of 2 (Poland, the United Kingdom depending on the regions.

  9. Phonon Emission from a Two-Dimensional Electron Gas.

    Science.gov (United States)

    Ouali, Fatma Fouzia

    Available from UMI in association with The British Library. Requires signed TDF. The work presented in this thesis is a study of the electron-phonon interaction in Si mosfets in both zero and magnetic fields. In the first part, a new experimental technique was proposed which allows, for the first time, the separation of the momentum scattering rate due to phonons from the scattering rate due to extrinsic processes. The technique was applied to a Si mosfet sample, in which weak localization effects are small, for temperatures up to 23K. It was found that, in this temperature range, the contribution of phonon scattering rate to momentum was negligible using the corrected values of T_{rm e} obtained by Akimov et al (1991), in contrast with the initial analysis obtained using the published data of Akimov et al (1991). In the second part, the location of the phonon emission was studied in a magnetic field of 6T over a wide range of powers (0.1 to 333 muW/mm ^2), and in particular in the quantum Hall regime (QHR). It was observed, for the first time, that in the QHR: (i) the energy dissipation occurs at the two diagonally opposite corners of the device, which correspond to the entry and exit points of the electrons and (ii) the dissipation in each of these corners is equal, i.e. the power dissipated in each is 50 +/- 1.3% of the total. These measurements are the first to demonstrate these effects and, although others have been made since, the precision of the symmetry of the dissipation remains the highest that has been reported.

  10. Instrumentation for Studies of Electron Emission and Charging From Insulators

    Science.gov (United States)

    Thomson, C. D.; Zavyalov, V.; Dennison, J. R.

    2004-01-01

    Making measurements of electron emission properties of insulators is difficult since insulators can charge either negatively or positively under charge particle bombardment. In addition, high incident energies or high fluences can result in modification of a material s conductivity, bulk and surface charge profile, structural makeup through bond breaking and defect creation, and emission properties. We discuss here some of the charging difficulties associated with making insulator-yield measurements and review the methods used in previous studies of electron emission from insulators. We present work undertaken by our group to make consistent and accurate measurements of the electron/ion yield properties for numerous thin-film and thick insulator materials using innovative instrumentation and techniques. We also summarize some of the necessary instrumentation developed for this purpose including fast response, low-noise, high-sensitivity ammeters; signal isolation and interface to standard computer data acquisition apparatus using opto-isolation, sample-and-hold, and boxcar integration techniques; computer control, automation and timing using Labview software; a multiple sample carousel; a pulsed, compact, low-energy, charge neutralization electron flood gun; and pulsed visible and UV light neutralization sources. This work is supported through funding from the NASA Space Environments and Effects Program and the NASA Graduate Research Fellowship Program.

  11. Electron beam confinement and image contrast enhancement in near field emission scanning electron microscopy.

    Science.gov (United States)

    Kirk, T L; De Pietro, L G; Pescia, D; Ramsperger, U

    2009-04-01

    In conventional scanning electron microscopy (SEM), the lateral resolution is limited by the electron beam diameter impinging on the specimen surface. Near field emission scanning electron microscopy (NFESEM) provides a simple means of overcoming this limit; however, the most suitable field emitter remains to be determined. NFESEM has been used in this work to investigate the W (110) surface with single-crystal tungsten tips of (310), (111), and (100)-orientations. The topographic images generated from both the electron intensity variations and the field emission current indicate higher resolution capabilities with decreasing tip work function than with polycrystalline tungsten tips. The confinement of the electron beam transcends the resolution limitations of the geometrical models, which are determined by the minimum beam width.

  12. Secondary electron emission yield on poled silica based thick films

    DEFF Research Database (Denmark)

    Braga, D.; Poumellec, B.; Cannas, V.

    2004-01-01

    injection, we pointed out an electric field 0.5 µm below the surface for our poling conditions and directed in the same direction as the external field applied during the poling process. Then, the dependence of on the injected dose of electrons allows us to deduce that the poling process disturbs the glass......Studies on the distribution of the electric field produced by a thermal poling process in a layer of Ge-doped silica on silicon substrate, by using secondary electron emission yield (SEEY) measurements () are presented. Comparing 0 between poled and unpoled areas, the SEEY at the origin of electron...... structure strongly enough for leading to a weak conductivity. It is then easy to display the poled areas. We have also pointed out an effect of the electric properties of the glass on the measurements obtained with the Electron Probe for MicroAnalysis....

  13. Calibration of electron cyclotron emission radiometer for KSTAR.

    Science.gov (United States)

    Kogi, Y; Jeong, S H; Lee, K D; Akaki, K; Mase, A; Kuwahara, D; Yoshinaga, T; Nagayama, Y; Kwon, M; Kawahata, K

    2010-10-01

    We developed and installed an electron cyclotron emission radiometer for taking measurements of Korea Superconducting Tokamak Advanced Research (KSTAR) plasma. In order to precisely measure the absolute value of electron temperatures, a calibration measurement of the whole radiometer system was performed, which confirmed that the radiometer has an acceptably linear output signal for changes in input temperature. It was also found that the output power level predicted by a theoretical calculation agrees with that obtained by the calibration measurement. We also showed that the system displays acceptable noise-temperature performance around 0.23 eV.

  14. Chandra ACIS Observations of Jovian X-Ray Emission

    Science.gov (United States)

    Garmire, Gordon; Elsner, Ronald; Feigelson, Eric; Ford, Peter; Gladstone, G. Randall; Hurley, Kevin; Metzger, Albert; Waite, J. Hunter, Jr.; Whitaker, Ann F. (Technical Monitor)

    2001-01-01

    On November 25 and 26, 1999, the Chandra X-ray spacecraft conducted a set of four 19,000 sec observations of Jupiter. The ACIS-S instrument configuration was used for its good low energy efficiency and spatial resolution. An anomalous response was obtained which was subsequently attributed to strong jovian infrared radiation penetrating the detector and piling up spurious events across the entire X-ray range. However, the pre-observation establishment of an offsetting bias field has allowed the recovery of data from that portion of Jupiter's disc which remained within the elevated portion of the bias field during the observation. This ranges from fewer than 3000 sec to the entire observing time for about 10% of the planet. Auroral emission is seen near both poles in each observation. The northern aurora ia overall more intense than the southern, consistent with prior Einstein and ROSAT Observatory results. The southern aurora shows more modulation with Jupiter's rotation than the northern. Spatial resolution has been improved by at least a factor of two over prior measurements but convincing evidence of structure has not been seen. Lower latitude emission, first observed by ROSAT, is confirmed with flux levels averaging more than a factor of five below peak auroral values. Pronounced variation in the observed emission has occurred over the observing period. The spectral response extends from 0.24 keV, below which noise dominates, to about 1.2 keV. For all four observations the spectrum is clearly enhanced between 0.45 and 0.85 keV. This is apparently unequivocal evidence that Jupiter's X-ray emission is the result of oxygen and perhaps sulfur ions precipitating into the planet's atmosphere, where they undergo charge exchange interactions. The identification of specific transitions lines in the spectrum is among the ongoing efforts. A bremsstrahlung component has not yet been identified.

  15. SOLAR FLARE CHROMOSPHERIC LINE EMISSION: COMPARISON BETWEEN IBIS HIGH-RESOLUTION OBSERVATIONS AND RADIATIVE HYDRODYNAMIC SIMULATIONS

    Energy Technology Data Exchange (ETDEWEB)

    Costa, Fatima Rubio da; Petrosian, Vahé [Department of Physics, Stanford University, Stanford, CA 94305 (United States); Kleint, Lucia [University of Applied Sciences and Arts Northwestern Switzerland, 5210 Windisch (Switzerland); Dalda, Alberto Sainz [Stanford-Lockheed Institute for Space Research, Stanford University, HEPL, 466 Via Ortega, Stanford, CA 94305 (United States); Liu, Wei, E-mail: frubio@stanford.edu [Lockheed Martin Solar and Astrophysics Laboratory, 3251 Hanover Street, Palo Alto, CA 94304 (United States)

    2015-05-01

    Solar flares involve impulsive energy release, which results in enhanced radiation over a broad spectral range and a wide range of heights. In particular, line emission from the chromosphere can provide critical diagnostics of plasma heating processes. Thus, a direct comparison between high-resolution spectroscopic observations and advanced numerical modeling results could be extremely valuable, but has not yet been attempted. In this paper, we present such a self-consistent investigation of an M3.0 flare observed by the Dunn Solar Telescope’s Interferometric Bi-dimensional Spectrometer (IBIS) on 2011 September 24 which we have modeled using the radiative hydrodynamic code RADYN. We obtained images and spectra of the flaring region with IBIS in Hα 6563 Å and Ca ii 8542 Å, and with RHESSI in X-rays. The latter observations were used to infer the non-thermal electron population, which was passed to RADYN to simulate the atmospheric response to electron collisional heating. We then synthesized spectral lines and compared their shapes and intensities to those observed by IBIS and found a general agreement. In particular, the synthetic Ca ii 8542 Å profile fits well to the observed profile, while the synthetic Hα profile is fainter in the core than for the observation. This indicates that Hα emission is more responsive to the non-thermal electron flux than the Ca ii 8542 Å emission. We suggest that it is necessary to refine the energy input and other processes to resolve this discrepancy.

  16. Upper Limits on O VI Emission from Voyager Observations

    Indian Academy of Sciences (India)

    R. Narasimhan (Krishtel eMaging) 1461 1996 Oct 15 13:05:22

    The data processing is described in Murthy et al. (1999) and resulted in 426 obser- vations of the ... We detect no O VI emission in any of 426 UVS observations of the diffuse radiation field but do set upper limits on such ... Assuming that the emitting gas has a solar abundance of helium atoms and that the hydrogen and ...

  17. Backscattered electron emission after proton impact on carbon and gold films: Experiments and simulations

    Science.gov (United States)

    Hespeels, F.; Heuskin, A. C.; Scifoni, E.; Kraemer, M.; Lucas, S.

    2017-06-01

    This work aims at measuring the proton induced secondary electron energy spectra from nanometer thin films. Backscattered electron energy spectra were measured within an energy range from 0 to 600 eV using a Retarding Field Analyser (RFA). This paper presents energy spectra obtained for proton (0.5 MeV; 1 MeV; 1.5 MeV; 2 MeV) irradiation of thin carbon films (50 and 100 nm thick) and thin gold film (200 nm). These experimental spectra were compared with Monte Carlo simulations based on TRAX code and Geant4 simulation toolkit. Good agreement between experimental, TRAX and Geant4 results were observed for the carbon target. For the gold target, we report major differences between both Monte Carlo environments. Limitation of Geant4 models for low energy electron emission was highlighted. On the contrary, TRAX simulations present encouraging results for the modeling of low-energy electron emission from gold target.

  18. Backscattered electron emission after proton impact on carbon and gold films: Experiments and simulations

    Energy Technology Data Exchange (ETDEWEB)

    Hespeels, F.; Heuskin, A.C. [University of Namur, PMR, 61 rue de Bruxelles, B-5000 Namur (Belgium); Scifoni, E. [TIFPA-INFN, Trento Institute for Fundamental Physics and Applications, Via Sommarive 14, I-38123 Trento (Italy); GSI-Helmholtzzentrum für Schwerionenforschung, Biophysik, Max Planck-Strasse 1, D-64291 Darmstadt (Germany); Kraemer, M. [GSI-Helmholtzzentrum für Schwerionenforschung, Biophysik, Max Planck-Strasse 1, D-64291 Darmstadt (Germany); Lucas, S., E-mail: stephane.lucas@unamur.be [University of Namur, PMR, 61 rue de Bruxelles, B-5000 Namur (Belgium)

    2017-06-15

    This work aims at measuring the proton induced secondary electron energy spectra from nanometer thin films. Backscattered electron energy spectra were measured within an energy range from 0 to 600 eV using a Retarding Field Analyser (RFA). This paper presents energy spectra obtained for proton (0.5 MeV; 1 MeV; 1.5 MeV; 2 MeV) irradiation of thin carbon films (50 and 100 nm thick) and thin gold film (200 nm). These experimental spectra were compared with Monte Carlo simulations based on TRAX code and Geant4 simulation toolkit. Good agreement between experimental, TRAX and Geant4 results were observed for the carbon target. For the gold target, we report major differences between both Monte Carlo environments. Limitation of Geant4 models for low energy electron emission was highlighted. On the contrary, TRAX simulations present encouraging results for the modeling of low-energy electron emission from gold target.

  19. Laser-initiated explosive electron emission from flat germanium crystals

    Energy Technology Data Exchange (ETDEWEB)

    Porshyn, V., E-mail: porshyn@uni-wuppertal.de; Mingels, S.; Lützenkirchen-Hecht, D.; Müller, G. [Faculty of Mathematics and Natural Sciences, Physics Department, University of Wuppertal, Wuppertal 42119 (Germany)

    2016-07-28

    Flat Sb-doped germanium (100) crystals were investigated in the triode configuration under pulsed tunable laser illumination (pulse duration t{sub laser} = 3.5 ns and photon energy hν = 0.54–5.90 eV) and under DC voltages <10{sup 4} V. Large bunch charges up to ∼1 μC were extracted from the cathodes for laser pulses >1 MW/cm{sup 2} corresponding to a high quantum efficiency up to 3.3% and cathode currents up to 417 A. This laser-induced explosive electron emission (EEE) from Ge was characterized by its voltage-, laser power- and hν-sensitivity. The analysis of the macroscopic surface damage caused by the EEE is included as well. Moreover, we have carried out first direct measurements of electron energy distributions produced during the EEE from the Ge samples. The measured electron spectra hint for electron excitations to the vacuum level of the bulk and emission from the plasma plume with an average kinetic energy of ∼0.8 eV.

  20. Secondary electron emission yield from high aspect ratio carbon velvet surfaces

    Science.gov (United States)

    Jin, Chenggang; Ottaviano, Angelica; Raitses, Yevgeny

    2017-11-01

    The plasma electrons bombarding a plasma-facing wall surface can induce secondary electron emission (SEE) from the wall. A strong SEE can enhance the power losses by reducing the wall sheath potential and thereby increasing the electron flux from the plasma to the wall. The use of the materials with surface roughness and the engineered materials with surface architecture is known to reduce the effective SEE by trapping the secondary electrons. In this work, we demonstrate a 65% reduction of SEE yield using a velvet material consisting of high aspect ratio carbon fibers. The measurements of SEE yield for different velvet samples using the electron beam in vacuum demonstrate the dependence of the SEE yield on the fiber length and the packing density, which is strongly affected by the alignment of long velvet fibers with respect to the electron beam impinging on the velvet sample. The results of SEE measurements support the previous observations of the reduced SEE measured in Hall thrusters.

  1. Scanning electron microscopic observations on bone.

    Science.gov (United States)

    Anderson, C; Danylchuk, K D

    1977-01-01

    The maceration technique employed in the preparation of specimens of bone for museum purposes has also been found to be of use in the preparation of fresh specimens for study with the scanning electron microscope. The technique requires less technical supervision, permits a greater underprocessing to overprocessing margin, and allows comparability of recent biopsy material with previously macerated bone specimens with no less detail than that found by other authors using other techniques on biopsy material.

  2. Free-electron laser emission architecture impact on EUV lithography

    Science.gov (United States)

    Hosler, Erik R.; Wood, Obert R.; Barletta, William A.

    2017-03-01

    Laser-produced plasma (LPP) EUV sources have demonstrated approximately 125 W at customer sites, establishing confidence in EUV lithography as a viable manufacturing technology. However, beyond the 7 nm technology node existing scanner/source technology must enable higher-NA imaging systems (requiring increased resist dose and providing half-field exposures) and/or EUV multi-patterning (requiring increased wafer throughput proportional to the number of exposure passes. Both development paths will require a substantial increase in EUV source power to maintain the economic viability of the technology, creating an opportunity for free-electron laser (FEL) EUV sources. FEL-based EUV sources offer an economic, high-power/single-source alternative to LPP EUV sources. Should free-electron lasers become the preferred next generation EUV source, the choice of FEL emission architecture will greatly affect its operational stability and overall capability. A near-term industrialized FEL is expected to utilize one of the following three existing emission architectures: (1) selfamplified spontaneous emission (SASE), (2) regenerative amplification (RAFEL), or (3) self-seeding (SS-FEL). Model accelerator parameters are put forward to evaluate the impact of emission architecture on FEL output. Then, variations in the parameter space are applied to assess the potential impact to lithography operations, thereby establishing component sensitivity. The operating range of various accelerator components is discussed based on current accelerator performance demonstrated at various scientific user facilities. Finally, comparison of the performance between the model accelerator parameters and the variation in parameter space provides a means to evaluate the potential emission architectures. A scorecard is presented to facilitate this evaluation and provide a framework for future FEL design and enablement for EUV lithography applications.

  3. Field-emission cathode gating for rf electron guns

    Directory of Open Access Journals (Sweden)

    J. W. Lewellen

    2005-03-01

    Full Text Available We present a novel method of combining the most desirable characteristics of thermionic-cathode and photocathode rf guns, using a field-emission cathode and multiple rf frequencies. Simulations indicate that extremely low-emittance beams (on the order of 2 nm normalized emittance at moderate beam currents (1 mA and beam energies of ∼2  MeV can be obtained using this technique. The resulting gun design promises to be useful as a driver source for a number of applications, including high-voltage electron microscopy, precision electron-beam welding, and long-wavelength (THz radiation generation; we include performance calculations for the electron microscopy and precision welding applications.

  4. Field-emission cathode gating for rf electron guns

    Science.gov (United States)

    Lewellen, J. W.; Noonan, J.

    2005-03-01

    We present a novel method of combining the most desirable characteristics of thermionic-cathode and photocathode rf guns, using a field-emission cathode and multiple rf frequencies. Simulations indicate that extremely low-emittance beams (on the order of 2 nm normalized emittance) at moderate beam currents (1 mA) and beam energies of ˜2 MeV can be obtained using this technique. The resulting gun design promises to be useful as a driver source for a number of applications, including high-voltage electron microscopy, precision electron-beam welding, and long-wavelength (THz) radiation generation; we include performance calculations for the electron microscopy and precision welding applications.

  5. Einstein Observations of X-ray emission from A stars

    Science.gov (United States)

    Golub, L.; Harnden, F. R., Jr.; Maxson, C. W.; Vaiana, G. S.; Snow, T. P., Jr.; Rosner, R.; Cash, W. C., Jr.

    1983-01-01

    Results are reported from the combined CfA Stellar Survey of selected bright A stars and an Einstein Guest Observer program for Ap and Am stars. In an initial report of results from the CfA Stellar Surveys by Vaiana et al. (1981) it was noted that the spread in observed X-ray luminosities among the few A stars observed was quite large. The reasons for this large spread was studied by Pallavicini et al. (1981). It was found that the X-ray emission from normal stars is related very strongly to bolometric luminosity for early-type stars and to rotation rate for late-type stars. However, an exception to this rule has been the apparently anomalous behavior of A star X-ray emission, for which the large spread in luminosity showed no apparent correlation with either bolometric luminosity or stellar rotation rate. In the present study, it is shown that the level of emission from normal A stars agrees with the correlation observed for O and B stars.

  6. Electron emission from MOS electron emitters with clean and cesium covered gold surface

    DEFF Research Database (Denmark)

    Nielsen, Gunver; Thomsen, Lasse Bjørchmar; Johansson, Martin

    2009-01-01

    characteristics have been investigated. It is known, that deposition of an alkali metal on the emitting surface lowers the work function and increases the emission efficiency. For increasing Cs coverages the surface has been characterized by X-ray Photoelectron Spectroscopy (XPS), Ion Scattering Spectroscopy (ISS......) and work function measurements. Energy spectra of electron emission from the devices under an applied bias voltage have been recorded for the clean Au surface and for two Cs coverages and simultaneous work function curves have been obtained. The electron emission onset is seen to appear at the surface work...... function. A method for cleaning the ex situ deposited Au top electrodes to a degree satisfactory to surface science studies has been developed, and a threshold for oxide damage by low-energy ion exposure between 0.5 and 1 keV has been determined....

  7. XMM-Newton Observations of Solar Wind Charge Exchange Emission

    Science.gov (United States)

    Snowden, S. L.; Collier, M. R.; Kuntz, K. D.

    2004-01-01

    We present an XMM-Newton spectrum of diffuse X-ray emission from within the solar system. The spectrum is dominated by O VII and O VIII lines at 0.57 keV and 0.65 keV, O VIII (and possibly Fe XVII) lines at approximately 0.8 keV, Ne IX lines at approximately 0.92 keV, and Mg XI lines at approximately 1.35 keV. This spectrum is consistent with what is expected from charge exchange emission between the highly ionized solar wind and either interstellar neutrals in the heliosphere or material from Earth's exosphere. The emission is clearly seen as a low-energy ( E less than 1.5 keV) spectral enhancement in one of a series of observations of the Hubble Deep Field North. The X-ray enhancement is concurrent with an enhancement in the solar wind measured by the ACE satellite. The solar wind enhancement reaches a flux level an order of magnitude more intense than typical fluxes at 1 AU, and has ion ratios with significantly enhanced higher ionization states. Whereas observations of the solar wind plasma made at a single point reflect only local conditions which may only be representative of solar wind properties with spatial scales ranging from less than half of an Earth radii (approximately 10 s) to 100 Earth radii, X-ray observations of solar wind charge exchange are remote sensing measurements which may provide observations which are significantly more global in character. Besides being of interest in its own right for studies of the solar system, this emission can have significant consequences for observations of more cosmological objects. It can provide emission lines at zero redshift which are of particular interest (e.g., O VII and O VIII) in studies of diffuse thermal emission, and which can therefore act as contamination in objects which cover the entire detector field of view. We propose the use of solar wind monitoring data, such as from the ACE and Wind spacecraft, as a diagnostic to screen for such possibilities.

  8. Influence of the secondary electron emission on the characteristics of radio frequency plasmas

    Directory of Open Access Journals (Sweden)

    Bojarov Aleksandar

    2011-01-01

    Full Text Available In this paper the influence of secondary emission on the characteristics of RF plasmas has been studied. An asymmetrical dual-frequency capacitively coupled plasma reactor has been modeled with one dimensional PIC/MCC (Particle in Cell with Implemented Monte Carlo Collisions code. The main feature of the modeling code represents the realistic model of the ion-induced secondary electron emission. Secondary emission of electrons is one of the important processes that effects the characteristics of rf plasmas. For modeling the secondary yield per ion, we have used equations proposed by Phelps and Petrović (Plasma Sources Sci. Technol. 8 (1999 R21-R44 for differently treated metal surfaces. In the model, the energy dependence of the yields per ion for differently treated metal surfaces has been implemented. Results are compared for yields for the so called “dirty” and “clean” surfaces, and the spatial profiles of charged particles and ion energy distributions were observed. The simulation results indicate that the plasma characteristics are greatly affected by the ion-induced secondary emission, changing the overall parameters of dual-frequency capacitively coupled plasma reactors especially in applications as etching devices. Conclusion is that an exact model of the secondary electron emission should be included, as to ensure better agreement between simulation and experiment.

  9. Observation of plasma microwave emission during the injection of supersonic plasma flows into magnetic arch

    Science.gov (United States)

    Viktorov, Mikhail; Mansfeld, Dmitry; Vodopyanov, Alexander; Golubev, Sergey

    2017-10-01

    Understanding of the energy transfer mechanisms from supersonic plasma flow into the thermal energy of plasma, waves and accelerated particles in the environment of planetary bow shocks and interplanetary shocks have been topical for many decades. Almost all mechanisms of energy dissipation in collisionless shock waves end with microscopic processes involving wave-particle interactions. Excitation of plasma waves in electron cyclotron frequency range plays an important role in the dissipation of bulk flow energy across the Earth bow shock. In the present work, the process of plasma deceleration during the injection of supersonic plasma flow across the magnetic field of an arched configuration is experimentally demonstrated. Pulsed plasma microwave emission in the electron cyclotron frequency range is observed. It is shown that the frequency spectrum of plasma emission is determined by the position of the deceleration region in the magnetic field of the magnetic arc and its bandwidth is defined by the magnetic field inhomogeneity in the deceleration region. The observed emission can be related to the cyclotron mechanism of wave generation by non-equilibrium energetic electrons in the dense plasma, especially excitation of electron Bernstein waves. The work was supported by RFBR (Project No. 16-32-60056).

  10. From the physics of secondary electron emission to image contrasts in scanning electron microscopy.

    Science.gov (United States)

    Cazaux, Jacques

    2012-01-01

    Image formation in scanning electron microscopy (SEM) is a combination of physical processes, electron emissions from the sample, and of a technical process related to the detection of a fraction of these electrons. For the present survey of image contrasts in SEM, simplified considerations in the physics of the secondary electron emission yield, δ, are combined with the effects of a partial collection of the emitted secondary electrons. Although some consideration is initially given to the architecture of modern SEM, the main attention is devoted to the material contrasts with the respective roles of the sub-surface and surface compositions of the sample, as well as with the roles of the field effects in the vacuum gap. The recent trends of energy filtering in normal SEM and the reduction of the incident energy to a few electron volts in very low-energy electron microscopy are also considered. For an understanding by the SEM community, the mathematical expressions are explained with simple physical arguments.

  11. C2 emission features in the Red Rectangle. A combined observational laboratory study

    Science.gov (United States)

    Wehres, N.; Romanzin, C.; Linnartz, H.; van Winckel, H.; Tielens, A. G. G. M.

    2010-07-01

    Context. The Red Rectangle proto-planetary nebula (HD 44179) is known for a number of rather narrow emission features superimposed on a broad extended red emission (ERE) covering the 5000-7500 Å regime. The origin of these emission features is unknown. Aims: The aim of the present work is to search for potential carriers by combining new observational and laboratory data. This also allows to interpret spectral emission features in terms of actual physical conditions like temperature and density constraints and to trace chemical processes in the outflows of the Red Rectangle. Methods: Observational spectra have been obtained with the EMMI-NTT at offsets of 3'', 6'', 7'', 11'', 16'' and 20'' distance to the central star HD 44179. The spectra are compared to the outcome of a time-gated laser induced fluorescence laboratory study of an expanding acetylene plasma using a special supersonic pin-hole discharge source. With this set-up the hydrocarbon chemistry in the Red Rectangle nebula is simulated under laboratory controlled conditions. The plasma source has the unique feature to generate electronically and vibrationally excited species at low rotational temperatures. The comparison is facilitated by a simple model for fluorescent emission in the nebula. Results: Two of the astronomically observed narrow emission bands can be assigned as originating from unresolved rovibronic progressions within the d3Π_g → a3Π_u Swan system of the C2 radical. The band appearance corresponds to a rotational temperature between 200 and 1000 K. The emission is driven by absorption in the C2 Phillips bands followed by intersystem crossing from the singlet to the triplet state and pumping in the Swan bands. Conclusions: These observations imply an active (photo)chemistry in the ejecta of the Red Rectangle. Based on observations collected at the European Southern Observatory, Chile. Program ID: 080.C-0814(A).

  12. Semi-shunt field emission in electronic devices

    Energy Technology Data Exchange (ETDEWEB)

    Karpov, V. G., E-mail: victor.karpov@utoledo.edu [Department of Physics and Astronomy, University of Toledo, Toledo, Ohio 43606 (United States); Shvydka, Diana, E-mail: diana.shvydka@utoledo.edu [Department of Radiation Oncology, University of Toledo, Toledo, Ohio 43606 (United States)

    2014-08-04

    We introduce a concept of semi-shunts representing needle shaped metallic protrusions shorter than the distance between a device electrodes. Due to the lightening rod type of field enhancement, they induce strong electron emission. We consider the corresponding signature effects in photovoltaic applications; they are: low open circuit voltages and exponentially strong random device leakiness. Comparing the proposed theory with our data for CdTe based solar cells, we conclude that stress can stimulate semi-shunts' growth making them shunting failure precursors. In the meantime, controllable semi-shunts can play a positive role mitigating the back field effects in photovoltaics.

  13. Method of electron emission control in RF guns

    CERN Document Server

    Khodak, I V

    2001-01-01

    The electron emission control method for a RF gun is considered.According to the main idea of the method,the additional resonance system is created in a cathode region where the RF field strength could be varied using the external pulse equipment. The additional resonance system is composed of a coaxial cavity coupled with a RF gun cylindrical cavity via an axial hole. Computed results of radiofrequency and electrodynamic performances of such a two-cavity system and results of the RF gun model pilot study are presented in. Results of particle dynamics simulation are described.

  14. Effects of Thickness, Pulse Duration, and Size of Strip Electrode on Ferroelectric Electron Emission of Lead Zirconate Titanate Films

    Science.gov (United States)

    Yaseen, Muhammad; Ren, Wei; Chen, Xiaofeng; Feng, Yujun; Shi, Peng; Wu, Xiaoqing

    2017-11-01

    Sol-gel-derived lead zirconate titanate (PZT) thin-film emitters with thickness up to 9.8 μm have been prepared on Pt/TiO2/SiO2/Si wafer via chemical solution deposition with/without polyvinylpyrrolidone (PVP) modification, and the relationship between the film thickness and electron emission investigated. Notable electron emission was observed on application of a trigger voltage of 120 V for PZT film with thickness of 1.1 μm. Increasing the film thickness decreased the threshold field to initiate electron emission for non-PVP-modified films. In contrast, the electron emission behavior of PVP-modified films did not show significant dependence on film thickness, probably due to their porous structure. The emission current increased with decreasing strip width and space between strips. Furthermore, it was observed that increasing the duration of the applied pulse increased the magnitude of the emission current. The stray field on the PZT film thickness was also calculated and found to increase with increasing ferroelectric sample thickness. The PZT emitters were found to be fatigue free up to 105 emission cycles. Saturated emission current of around 25 mA to 30 mA was achieved for the electrode pattern used in this work.

  15. Electron Bernstein waves emission in the TJ--II Stellarator

    CERN Document Server

    García-Regaña, J M; Castejón, F; Caughman, J B O; Tereshchenko, M; Ros, A; Rasmussen, D A; Wilgen, J B

    2010-01-01

    Taking advantage of the electron Bernstein waves heating (EBWH) system of the TJ--II stellarator, an electron Bernstein emission (EBE) diagnostic was installed. Its purpose is to investigate the B--X--O radiation properties in the zone where optimum theoretical EBW coupling is predicted. An internal movable mirror shared by both systems allows us to collect the EBE radiation along the same line of sight that is used for EBW heating. The theoretical EBE has been calculated for different orientations of the internal mirror using the TRUBA code as ray tracer. A comparison with experimental data obtained in NBI discharges is carried out. The results provide a valuable information regarding the experimental O--X mode conversion window expected in the EBW heating experiments. Furthermore, the characterization of the radiation polarization shows evidence of the underlying B--X--O conversion process.

  16. Spectral evolution of soft x-ray emission from optically thin, high electron temperature platinum plasmas

    Directory of Open Access Journals (Sweden)

    Hiroyuki Hara

    2017-08-01

    Full Text Available The soft x-ray spectra of heavy element plasmas are frequently dominated by unresolved transition array (UTA emission. We describe the spectral evolution of an intense UTA under optically thin conditions in platinum plasmas. The UTA was observed to have a peak wavelength around 4.6 nm at line-of-sight averaged electron temperatures less than 1.4 keV at electron densities of (2.5–7.5 × 1013 cm−3. The UTA spectral structure was due to emission from 4d–4f transitions in highly charged ions with average charge states of q = 20–40. A numerical simulation successfully reproduced the observed spectral behavior.

  17. Spectral evolution of soft x-ray emission from optically thin, high electron temperature platinum plasmas

    Science.gov (United States)

    Hara, Hiroyuki; Ohashi, Hayato; Li, Bowen; Dunne, Padraig; O'Sullivan, Gerry; Sasaki, Akira; Suzuki, Chihiro; Tamura, Naoki; Sakaue, Hiroyuki A.; Kato, Daiji; Murakami, Izumi; Higashiguchi, Takeshi; LHD Experiment Group

    2017-08-01

    The soft x-ray spectra of heavy element plasmas are frequently dominated by unresolved transition array (UTA) emission. We describe the spectral evolution of an intense UTA under optically thin conditions in platinum plasmas. The UTA was observed to have a peak wavelength around 4.6 nm at line-of-sight averaged electron temperatures less than 1.4 keV at electron densities of (2.5-7.5) × 1013 cm-3. The UTA spectral structure was due to emission from 4d-4f transitions in highly charged ions with average charge states of q = 20-40. A numerical simulation successfully reproduced the observed spectral behavior.

  18. Angle-resolved 2D imaging of electron emission processes in atoms and molecules

    Energy Technology Data Exchange (ETDEWEB)

    Kukk, E.; Wills, A.A.; Langer, B.; Bozek, J.D.; Berrah, N.

    2004-09-02

    A variety of electron emission processes have been studied in detail for both atomic and molecular systems, using a highly efficient experimental system comprising two time-of-flight (TOF) rotatable electron energy analyzers and a 3rd generation synchrotron light source. Two examples are used here to illustrate the obtained results. Firstly, electron emissions in the HCL molecule have been mapped over a 14 eV wide photon energy range over the Cl 2p ionization threshold. Particular attention is paid to the dissociative core-excited states, for which the Auger electron emission shows photon energy dependent features. Also, the evolution of resonant Auger to the normal Auger decay distorted by post-collision interaction has been observed and the resonating behavior of the valence photoelectron lines studied. Secondly, an atomic system, neon, in which excitation of doubly excited states and their subsequent decay to various accessible ionic states has been studied. Since these processes only occurs via inter-electron correlations, the many body dynamics of an atom can be probed, revealing relativistic effects, surprising in such a light atom. Angular distribution of the decay of the resonances to the parity unfavored continuum exhibits significant deviation from the LS coupling predictions.

  19. Tropospheric Emission Spectrometer for the Earth Observing System

    Science.gov (United States)

    Glavich, Thomas A.; Beer, Reinhard

    1991-01-01

    A Tropospheric Emission Spectrometer (TES) for the Earth Observing System (EOS) series of polar-orbiting platforms is described. TES is aimed at studying tropospheric chemistry, in particular, the exchange of gases between the surface and the atmosphere, urban and regional pollution, acid rain precursors, sources and sinks of greenhouse gases, and the interchange of gases between the troposphere and the stratosphere. TES is a high-resolution (0.025/cm) infrared Fourier transform spectrometer operating in the passive thermal-emission mode in a very wide spectral range (600 to 4350/cm; 2.3 to 16.7 microns). TES has 32 spatial pixels in each of four optically conjugated linear detector arrays, each optimized for a different spectral region.

  20. Secondary-electron-emission spectroscopy of tungsten: Angular dependence and phenomenology

    DEFF Research Database (Denmark)

    Willis, Roy F.; Christensen, Niels Egede

    1978-01-01

    Angle-resolved energy-distribution measurements of secondary-electron emission (SEE) from metals reveal spectral fine structure that relates directly to the density distribution of the one-electron states throughout E-K→ space located above the vacuum level Ev. The angular dependence of the SEE s...... to electron emission phenomenology of metal surfaces, thereby establishing a relationship with recently developed low-energy electron diffraction, photoemission, and field-emission formalism....

  1. Chirped Auger electron emission due to field-assisted post-collision interaction

    Directory of Open Access Journals (Sweden)

    Bonitz M.

    2013-03-01

    Full Text Available We have investigated the Auger decay in the temporal domain by applying a terahertz streaking light field. Xenon and krypton atoms were studied by implementing the free-electron laser in Hamburg (FLASH as well as a source of high-order harmonic radiation combined with terahertz pulses from an optical rectification source. The observed linewidth asymmetries in the streaked spectra suggest a chirped Auger electron emission which is understood in terms of field-assisted post-collision interaction. The experimentally obtained results agree well with model calculations.

  2. Electrostatic Electron Cyclotron Waves Observed by the Plasma Wave Instrument on Board Polar

    Science.gov (United States)

    Menietti, J. D.; Pickett, J. S.; Gurnett, D. A.; Scudder, J. D.

    2001-01-01

    We report the results of an investigation of waves observed by the Polar spacecraft at high altitudes and latitudes and at frequencies just above the cyclotron frequency. These observations are made frequently when the spacecraft is over the polar cap as well as near the dayside cusp and near the nightside auroral region, and observations are made for ratios of plasma frequency to cyclotron frequency, f(sub p)/f(sub c) = 1. Using the six-channel high-frequency waveform receiver (HFWR) on board the spacecraft, which can provide three-axis electric and three-axis magnetic field measurements, we attempt to identify the wavemode of these emissions and investigate possible source mechanisms including low-energy electron beams. We further observe electromagnetic emission associated with upper hybrid waves near and within the plasmasphere. This emission is consistent with both Z and O modes.

  3. Observations of the Solar Continuum Radio Emission at Decameter Wavelengths

    Science.gov (United States)

    Brazhenko, Anatoliy I.; Mel'Nik, Valentin N.; Konovalenko, Alexander A.; Abranin, Edward P.; Dorovskyy, Vladimir V.; Vashchishin, Rostislav V.; Frantzusenko, Anatoly V.; Rucker, Helmut O.

    2010-01-01

    Results of study of the continuum radio emission of the Sun in the decameter range are presented. Observations were carried out with radio telescope URAN-2 in summer months in 2008-2009. Radio fluxes at frequencies 20 MHz and 25 MHz in frequency band 250 kHz were obtained during the time, when there were no active regions on the solar disk. Their average values for two years were 670 Jy and 850 Jy at frequencies 20 MHz and 25 MHz correspondingly. These fluxes are in agreement with high frequency values.

  4. Axial ion-electron emission microscopy of IC radiation hardness

    Science.gov (United States)

    Doyle, B. L.; Vizkelethy, G.; Walsh, D. S.; Swenson, D.

    2002-05-01

    A new system for performing radiation effects microscopy (REM) has been developed at Sandia National Laboratory in Albuquerque. This system combines two entirely new concepts in accelerator physics and nuclear microscopy. A radio frequency quadrupole (RFQ) linac is used to boost the energy of ions accelerated by a conventional Tandem Van de Graaff-Pelletron to velocities of 1.9 MeV/amu. The electronic stopping power for heavy ions is near a maximum at this velocity, and their range is ˜20 μm in Si. These ions therefore represent the most ionizing form of radiation in nature, and are nearly ideal for performing single event effects testing of integrated circuits. Unfortunately, the energy definition of the RFQ-boosted ions is rather poor (˜ a few %), which makes problematic the focussing of such ions to the submicron spots required for REM. To circumvent this problem, we have invented ion electron emission microscopy (IEEM). One can perform REM with the IEEM system without focussing or scanning the ion beam. This is because the position on the sample where each ion strikes is determined by projecting ion-induced secondary electrons at high magnification onto a single electron position sensitive detector. This position signal is then correlated with each REM event. The IEEM system is now mounted along the beam line in an axial geometry so that the ions pass right through the electron detector (which is annular), and all of the electrostatic lenses used for projection. The beam then strikes the sample at normal incidence which results in maximum ion penetration and removes a parallax problem experienced in an earlier system. Details of both the RFQ-booster and the new axial IEEM system are given together with some of the initial results of performing REM on Sandia-manufactured radiation hardened integrated circuits.

  5. Observation of isotropic electron temperature in the turbulent E region

    Directory of Open Access Journals (Sweden)

    S. Saito

    Full Text Available Using EISCAT radar data, we find that electrons are strongly heated in the magnetic field-line direction during high electric field events. The remote site data show that the electron temperature increases in almost the same way in the field-perpendicular direction; electron heating by E region plasma turbulence is isotropic. We discuss the implications of our observation for the "plasmon"-electron as well as the wave Joule heating models of the anomalous electron heating in the E region.

    Key words. Ionosphere (auroral ionosphere; plasma temperature and density; plasma waves and instabilities

  6. Secondary electron emission from plasma processed accelerating cavity grade niobium

    Science.gov (United States)

    Basovic, Milos

    Advances in the particle accelerator technology have enabled numerous fundamental discoveries in 20th century physics. Extensive interdisciplinary research has always supported further development of accelerator technology in efforts of reaching each new energy frontier. Accelerating cavities, which are used to transfer energy to accelerated charged particles, have been one of the main focuses of research and development in the particle accelerator field. Over the last fifty years, in the race to break energy barriers, there has been constant improvement of the maximum stable accelerating field achieved in accelerating cavities. Every increase in the maximum attainable accelerating fields allowed for higher energy upgrades of existing accelerators and more compact designs of new accelerators. Each new and improved technology was faced with ever emerging limiting factors. With the standard high accelerating gradients of more than 25 MV/m, free electrons inside the cavities get accelerated by the field, gaining enough energy to produce more electrons in their interactions with the walls of the cavity. The electron production is exponential and the electron energy transfer to the walls of a cavity can trigger detrimental processes, limiting the performance of the cavity. The root cause of the free electron number gain is a phenomenon called Secondary Electron Emission (SEE). Even though the phenomenon has been known and studied over a century, there are still no effective means of controlling it. The ratio between the electrons emitted from the surface and the impacting electrons is defined as the Secondary Electron Yield (SEY). A SEY ratio larger than 1 designates an increase in the total number of electrons. In the design of accelerator cavities, the goal is to reduce the SEY to be as low as possible using any form of surface manipulation. In this dissertation, an experimental setup was developed and used to study the SEY of various sample surfaces that were treated

  7. Secondary Electron Emission from Plasma Processed Accelerating Cavity Grade Niobium

    Energy Technology Data Exchange (ETDEWEB)

    Basovic, Milos [Old Dominion Univ., Norfolk, VA (United States)

    2016-05-01

    Advances in the particle accelerator technology have enabled numerous fundamental discoveries in 20th century physics. Extensive interdisciplinary research has always supported further development of accelerator technology in efforts of reaching each new energy frontier. Accelerating cavities, which are used to transfer energy to accelerated charged particles, have been one of the main focuses of research and development in the particle accelerator field. Over the last fifty years, in the race to break energy barriers, there has been constant improvement of the maximum stable accelerating field achieved in accelerating cavities. Every increase in the maximum attainable accelerating fields allowed for higher energy upgrades of existing accelerators and more compact designs of new accelerators. Each new and improved technology was faced with ever emerging limiting factors. With the standard high accelerating gradients of more than 25 MV/m, free electrons inside the cavities get accelerated by the field, gaining enough energy to produce more electrons in their interactions with the walls of the cavity. The electron production is exponential and the electron energy transfer to the walls of a cavity can trigger detrimental processes, limiting the performance of the cavity. The root cause of the free electron number gain is a phenomenon called Secondary Electron Emission (SEE). Even though the phenomenon has been known and studied over a century, there are still no effective means of controlling it. The ratio between the electrons emitted from the surface and the impacting electrons is defined as the Secondary Electron Yield (SEY). A SEY ratio larger than 1 designates an increase in the total number of electrons. In the design of accelerator cavities, the goal is to reduce the SEY to be as low as possible using any form of surface manipulation. In this dissertation, an experimental setup was developed and used to study the SEY of various sample surfaces that were treated

  8. Transition in discharge plasma of Hall thruster type in presence of secondary electron emissive surface

    Science.gov (United States)

    Schweigert, I. V.; Yadrenkin, M. A.; Fomichev, V. P.

    2017-11-01

    Modification of the sheath structure near the emissive plate placed in magnetized DC discharge plasma of Hall thruster type was studied in the experiment and in kinetic simulations. The plate is made from Al2O3 which has enhanced secondary electron emission yield. The energetic electrons emitted by heated cathode provide the volume ionization and the secondary electron emission from the plate. An increase of the electron beam energy leads to an increase of the secondary electron generation, which initiates the transition in sheath structure over the emissive plate.

  9. Radiation by energetic electrons accelerated by wave-particle interaction: a plausible mechanism for X-ray emission from the Venus mantle

    Energy Technology Data Exchange (ETDEWEB)

    Bingham, R. [STFC Rutherford Appleton Lab., Didcot, Oxon (United Kingdom). Space Science and Technology Dept.; Strathclyde Univ., Glasgow (United Kingdom). Physics Dept.; Quest, K.B. [California Univ., San Diego, La Jolla, CA (United States). ECE Dept.; Shapiro, V.D. [California Univ., San Diego, La Jolla, CA (United States). Physics Dept.; Kellett, B.J. [STFC Rutherford Appleton Lab., Didcot, Oxon (United Kingdom). Space Science and Technology Dept.

    2008-07-01

    In this paper it is argued that recently observed X-ray emission from non-magnetic planets (Dennerl et al., 2002) can be explained as a combination of bremsstrahlung and line K-shell radiation produced by the interaction of energetic electrons with the neutral atmosphere. Numerical simulations show that the modified two stream instability can generate energetic 100 eV electrons that are observed and these electrons can produce X-ray emission. (orig.)

  10. Radiation by energetic electrons accelerated by wave-particle interaction: a plausible mechanism for x-ray emission from the Venus mantle

    Directory of Open Access Journals (Sweden)

    R. Bingham

    2008-07-01

    Full Text Available In this paper it is argued that recently observed x-ray emission from non-magnetic planets (Dennerl et al., 2002 can be explained as a combination of bremsstrahlung and line K-shell radiation produced by the interaction of energetic electrons with the neutral atmosphere. Numerical simulations show that the modified two stream instability can generate energetic 100 eV electrons that are observed and these electrons can produce x-ray emission.

  11. Enhancement of low-energy electron emission in 2D radioactive films

    Science.gov (United States)

    Pronschinske, Alex; Pedevilla, Philipp; Murphy, Colin J.; Lewis, Emily A.; Lucci, Felicia R.; Brown, Garth; Pappas, George; Michaelides, Angelos; Sykes, E. Charles H.

    2015-09-01

    High-energy radiation has been used for decades; however, the role of low-energy electrons created during irradiation has only recently begun to be appreciated. Low-energy electrons are the most important component of radiation damage in biological environments because they have subcellular ranges, interact destructively with chemical bonds, and are the most abundant product of ionizing particles in tissue. However, methods for generating them locally without external stimulation do not exist. Here, we synthesize one-atom-thick films of the radioactive isotope 125I on gold that are stable under ambient conditions. Scanning tunnelling microscopy, supported by electronic structure simulations, allows us to directly observe nuclear transmutation of individual 125I atoms into 125Te, and explain the surprising stability of the 2D film as it underwent radioactive decay. The metal interface geometry induces a 600% amplification of low-energy electron emission (targeted nanoparticle therapies.

  12. Tachyonic Cherenkov emission from Jupiter's radio electrons

    Energy Technology Data Exchange (ETDEWEB)

    Tomaschitz, Roman, E-mail: tom@geminga.org

    2013-12-17

    Tachyonic Cherenkov radiation from inertial relativistic electrons in the Jovian radiation belts is studied. The tachyonic modes are coupled to a frequency-dependent permeability tensor and admit a negative mass-square, rendering them superluminal and dispersive. The superluminal radiation field can be cast into Maxwellian form, using 3D field strengths and inductions, and the spectral densities of tachyonic Cherenkov radiation are derived. The negative mass-square gives rise to a longitudinal flux component. A spectral fit to Jupiter's radio spectrum, inferred from ground-based observations and the Cassini 2001 fly-by, is performed with tachyonic Cherenkov flux densities averaged over a thermal electron population.

  13. Space-Time mapping of terahertz-induced electron field emission

    DEFF Research Database (Denmark)

    Lange, Simon Lehnskov; Kristensen, Thea M. B.; Iwaszczuk, Krzysztof

    2017-01-01

    We present simulations and experiments showing how THz induced electron field emission from gold antennas can be mapped indirectly in space and time. Our simulations predict the spatiotemporal electron distribution after single-cycle THz-induced field emission. Two different experiments validate...... this through a time-accumulated, spatial electron mapping due to both short- and long-time irradiation with THz transients....

  14. Rosetta Alice/VIRTIS observations of the water vapour UV electroglow emissions around comet 67P/Churyumov-Gerasimenko

    Science.gov (United States)

    Chaufray, J.-Y.; Bockelée-Morvan, D.; Bertaux, J.-L.; Erard, S.; Feldman, P. D.; Capaccioni, F.; Schindhelm, E.; Leyrat, C.; Parker, J.; Filacchione, G.; A'Hearn, M. F.; Feaga, L. M.; Noonan, J.; Keeney, B.; Steffl, A. J.; Stern, S. A.; Weaver, H. A.; Broiles, T.; Burch, J.; Clark, G.; Samara, M.

    2017-07-01

    Several UV emission lines of the coma of 67P/Churyumov-Gerasimenko have been observed by Alice/Rosetta before the 67P/CG perihelion. The H and O emissions are mainly produced by impact dissociation of water molecules by suprathermal electrons. In this paper, we explore further the electron dissociative excitation of H2O to produce the UV emissions by using simultaneous observations of water and H Lyman β done by the VIRTIS-H and Alice instruments during four periods of time in 2014 December, 2015 March and 2015 May. We used simple theoretical considerations to link the UV brightness to the water vapour column density. Two cases are studied. In the first case, we assume the suprathermal electron density is decreasing radially as the thermal electron population; in the second case, we assume the suprathermal electron density does not vary radially. The second case seems more consistent with the Rosetta Plasma Consortium Ion and Electron Sensor measurements during 2015 March and May. The efficiency of the electron dissociative excitation of H2O is lower during the three last periods of time studied compared to the first period in 2014 December. The variability of the efficiency of the electron dissociative excitation between the four studied periods is not simply inversely proportional to the square of the comet-Sun distance but is most likely associated with the variability of the suprathermal electron distribution.

  15. Ultralarge area MOS tunnel devices for electron emission

    DEFF Research Database (Denmark)

    Thomsen, Lasse Bjørchmar; Nielsen, Gunver; Vendelbo, Søren Bastholm

    2007-01-01

    A comparative analysis of metal-oxide-semiconductor (MOS) capacitors by capacitance-voltage (C-V) and current-voltage (I-V) characteristics has been employed to characterize the thickness variations of the oxide on different length scales. Ultralarge area (1 cm(2)) ultrathin (similar to 5 nm oxide......) MOS capacitors have been fabricated to investigate their functionality and the variations in oxide thickness, with the use as future electron emission devices as the goal. I-V characteristics show very low leakage current and excellent agreement to the Fowler-Nordheim expression for the current...... density. Oxide thicknesses have been extracted by fitting a model based on Fermi-Dirac statistics to the C-V characteristics. By plotting I-V characteristics in a Fowler plot, a measure of the thickness of the oxide can be extracted from the tunnel current. These apparent thicknesses show a high degree...

  16. Alternative optical concept for electron cyclotron emission imaging.

    Science.gov (United States)

    Liu, J X; Milbourne, T; Bitter, M; Delgado-Aparicio, L; Dominguez, A; Efthimion, P C; Hill, K W; Kramer, G J; Kung, C; Kubota, S; Kasparek, W; Lu, J; Pablant, N A; Park, H; Tobias, B

    2014-11-01

    The implementation of advanced electron cyclotron emission imaging (ECEI) systems on tokamak experiments has revolutionized the diagnosis of magnetohydrodynamic (MHD) activities and improved our understanding of instabilities, which lead to disruptions. It is therefore desirable to have an ECEI system on the ITER tokamak. However, the large size of optical components in presently used ECEI systems have, up to now, precluded the implementation of an ECEI system on ITER. This paper describes a new optical ECEI concept that employs a single spherical mirror as the only optical component and exploits the astigmatism of such a mirror to produce an image with one-dimensional spatial resolution on the detector. Since this alternative approach would only require a thin slit as the viewing port to the plasma, it would make the implementation of an ECEI system on ITER feasible. The results obtained from proof-of-principle experiments with a 125 GHz microwave system are presented.

  17. Carboxylate Counteranions in Electronic Cigarette Liquids: Influence on Nicotine Emissions.

    Science.gov (United States)

    El-Hellani, Ahmad; El-Hage, Rachel; Salman, Rola; Talih, Soha; Shihadeh, Alan; Saliba, Najat A

    2017-08-21

    The wide pH range reported for electronic cigarette (ECIG) liquids indicates that nicotine may be present in one or more chemical forms. The nicotine form affects the bioavailability and delivery of nicotine from inhaled products. Protonated nicotine is normally associated with counteranions in tobacco products. The chemical and physical properties of counteranions may differently influence the nicotine form and emissions in ECIG aerosols. In this study, we examined how these anions influence nicotine emissions and their evaporation behavior and potential decomposition during ECIG operation. ECIG liquid solutions with equal nicotine concentration and pH but different counteranions (formate, acetate, and citrate) were prepared from analytical standards to assess the effect of the counteranion on nicotine partitioning. High performance liquid and gas chromatography methods were developed to determine the counteranions and the two protonated (NicH+) and free base (Nic) forms of nicotine in commercially available and standard solutions of ECIG liquids and aerosols. In commercial samples, acetate and citrate anions were detected. In standard solutions, both formate and acetate ions were found to evaporate intact, but citrate ion decomposed into formic acid and other products. This study also shows that the identity of the counteranion has no effect on total nicotine emission from ECIG in agreement with previous reports on tobacco cigarettes. However, the partitioning of aerosolized nicotine into NicH+ and Nic is anion-dependent even when the parent liquid pH is held constant. These results indicate that the anions found in a given ECIG product may influence the nicotine delivery profile to the user by enriching aerosols with free-base nicotine as in the case of polycarboxylic acids such as citric acid.

  18. Calculated ionization rates, ion densities, and airglow emission rates due to precipitating electrons in the nightside ionosphere of Mars

    Science.gov (United States)

    Haider, S. A.; Kim, J.; Nagy, A. F.; Keller, C. N.; Verigin, M. I.; Gringauz, K. I.; Shutte, N. M.; Szego, K.; Kiraly, P.

    1992-01-01

    The calculations presented in this paper clearly establish that the electron fluxes measured by the HARP instrument, carried on board Phobos 2, could cause significant electron impact ionization and excitation in the nightside atmosphere of Mars, if these electrons actually do precipitate. The calculated peak electron densities were found to be about a factor of 2 larger than the mean observed nightside densities, indicating that if a significant fraction of the measured electrons actually precipitate, they could be the dominant mechanism responsible for maintaining the nightside ionosphere. The calculated zenith column emission rates of the O I 5577-A and 6300-A and CO Cameron band emissions, due to electron impact and dissociative recombination mechanisms, were found to be significant.

  19. Secondary Electron Emission from Solid Hydrogen and Deuterium Resulting from Incidence of keV Electrons and Hydrogen Ions

    DEFF Research Database (Denmark)

    Sørensen, H.

    1977-01-01

    The secondary electron emission (SEE) coefficient δ was measured for solid hydrogen and deuterium resulting from the normal incidence of 0.5–3‐keV electrons and 4–10‐keV H+, H2+, H3+, and D3+ ions. The SEE coefficients for solid hydrogen are 60–70% of those for solid deuterium, and the coefficients...... or the stopping power of the incident particles. Measurements were also made for oblique incidence of H+ ions on solid deuterium for angles of incidence up to 75°. A correction could be made for the emission of secondary ions by also measuring the current calorimetrically. At largest energies, the angular....... The losses to molecular states will be largest for hydrogen, so that the SEE coefficients are smallest for solid hydrogen, as was observed. For the incidence of ions, the values of δ for the different molecular ions agree when the number of secondary electrons per incident atom is plotted versus the velocity...

  20. Low-energy plasma-cathode electron gun with a perforated emission electrode

    Science.gov (United States)

    Burdovitsin, Victor; Kazakov, Andrey; Medovnik, Alexander; Oks, Efim; Tyunkov, Andrey

    2017-11-01

    We describe research of influence of the geometric parameters of perforated electrode on emission parameters of a plasma cathode electron gun generating continuous electron beams at gas pressure 5-6 Pa. It is shown, that the emission current increases with increasing the hole diameters and decreasing the thickness of the perforated emission electrode. Plasma-cathode gun with perforated electron can provide electron extraction with an efficiency of up to 72 %. It is shown, that the current-voltage characteristic of the electron gun with a perforated emission electrode differs from that of similar guns with fine mesh grid electrode. The plasma-cathode electron gun with perforated emission electrode is used for electron beam welding and sintering.

  1. Quantum multiscattering interferences in collision-induced coherent electron emission from diatomic molecules by swift ion impact

    Science.gov (United States)

    Agueny, H.; Hansen, J. P.

    2016-11-01

    In the intramolecular scattering process, the interference between the rescattered electron waves emanating from each atomic center gives rise to additional oscillations superimposed on the Young-type oscillatory structure in the observed electron intensity. Here we explore numerically this behavior for coherent electron emission from the dimer Rb2 + by fast-moving highly charged ions, which is achieved by solving the two-dimensional time-dependent Schrödinger equation. Well-defined modulations with higher frequency are observed in the momentum distribution of the ejected electron, which are well reproduced by additional quantitative calculations based on the third-order Born series. This demonstrates without ambiguity the dynamic interference induced by multiple scattering paths of the electron prior to emission. Furthermore, the dependence of the phenomenon on the emission direction of the electron and the orientation of the molecular axis also is investigated. The phenomenon is not specific to Rb2 + as investigated in the present study, but is broadly applicable to other systems with sufficiently large internuclear distances, thus opening new prospects for the investigation of electron emission process from large systems.

  2. Electron cyclotron maser emission in coronal arches and solar radio type V bursts

    Energy Technology Data Exchange (ETDEWEB)

    Tang, J. F. [Xinjiang Astronomical Observatory, Chinese Academy of Sciences, 150 Science 1-Street, Urumqi, Xinjiang 830011 (China); Wu, D. J. [Purple Mountain Observatory, CAS, Nanjing 210008 (China); Tan, C. M., E-mail: jftang@xao.ac.cn [Key Laboratory of Solar Activity, National Astronomical Observatories, Chinese Academy of Sciences, Beijing 100012 (China)

    2013-12-10

    Solar radio type V bursts were classified as a special spectral class based on their moderately long duration, wide bandwidth, and sense of polarization opposite of associated type III bursts. However, type V bursts are also closely related to the preceding type III bursts. They have an approximately equal source height and the same dispersion of position with frequency. Electron cyclotron maser (ECM) instability driven by beam electrons has been used to explain type III bursts in recent years. We propose ECM emission as the physical process of type V solar radio bursts. According to the observed properties of type V and III bursts, we propose that energetic electrons in excited type V continuum are trapped in coronal loops, which are adjacent to the open field lines traced by type III electrons. With the proposed magnetic field configuration and the ECM emission mechanism, the observed properties of type V bursts, such as long duration, wide bandwidth, and opposite sense of polarization can be reasonably explained by our model.

  3. Differential electron emission from polycyclic aromatic hydrocarbon molecules under fast ion impact.

    Science.gov (United States)

    Biswas, Shubhadeep; Champion, Christophe; Weck, P F; Tribedi, Lokesh C

    2017-07-17

    Interaction between polycyclic aromatic hydrocarbon (PAH) molecule and energetic ion is a subject of interest in different areas of modern physics. Here, we present measurements of energy and angular distributions of absolute double differential electron emission cross section for coronene (C24H12) and fluorene (C13H10) molecules under fast bare oxygen ion impact. For coronene, the angular distributions of the low energy electrons are quite different from that of simpler targets like Ne or CH4, which is not the case for fluorene. The behaviour of the higher electron energy distributions for both the targets are similar to that for simple targets. In case of coronene, a clear signature of plasmon resonance is observed in the analysis of forward-backward angular asymmetry of low energy electron emission. For fluorene, such signature is not identified probably due to lower oscillator strength of plasmon compared to the coronene. The theoretical calculation based on the first-order Born approximation with correct boundary conditions (CB1), in general, reproduced the experimental observations qualitatively, for both the molecules, except in the low energy region for coronene, which again indicates the role of collective excitation. Single differential and total cross sections are also deduced. An overall comparative study is presented.

  4. A Technique for In Situ Ballistic Electron Emission Microscopy

    Science.gov (United States)

    Balsano, Robert; Garramone, John; Labella, Vincent

    2012-02-01

    Ballistic electron emission microscopy (BEEM) is a scanning tunneling microscopy (STM) technique that can measure transport of hot electrons through materials and interfaces with high spatial and energetic resolution. BEEM requires an additional contact to ground the metal base layer of a metal semiconductor junction. Performing BEEM in situ with the sample fabrication requires a custom built STM or modifying a commercial one to facilitate the extra contact, which leaves the technique to highly trained experts. This poster will describe our work to develop a special silicon substrate that has the extra contact built in to enable in situ BEEM without modifications to the STM. Electrically isolated contact traces are lithographically patterned ex situ onto the silicon substrate and connected to the BEEM sample plate which is then inserted into the ultra-high vacuum chamber. The metal is then deposited through a shadow mask and then mounted in situ onto the STM for BEEM measurements. BEEM measurements comparing both in situ and ex situ deposited films will be presented.

  5. Measurements of the Secondary Electron Emission of Some Insulators

    CERN Document Server

    Bozhko, Y.; Hilleret, N.

    2013-01-01

    Charging up the surface of an insulator after beam impact can lead either to reverse sign of field between the surface and collector of electrons for case of thick sample or appearance of very high internal field for thin films. Both situations discard correct measurements of secondary electron emission (SEE) and can be avoided via reducing the beam dose. The single pulse method with pulse duration of order of tens microseconds has been used. The beam pulsing was carried out by means of an analog switch introduced in deflection plate circuit which toggles its output between "beam on" and "beam off" voltages depending on level of a digital pulse. The error in measuring the beam current for insulators with high value of SEE was significantly reduced due to the use for this purpose a titanium sample having low value of the SEE with DC method applied. Results obtained for some not coated insulators show considerable increase of the SEE after baking out at 3500C what could be explained by the change of work functi...

  6. Modeling Atmospheric Emission for CMB Ground-based Observations

    Science.gov (United States)

    Errard, J.; Ade, P. A. R.; Akiba, Y.; Arnold, K.; Atlas, M.; Baccigalupi, C.; Barron, D.; Boettger, D.; Borrill, J.; Chapman, S.; Chinone, Y.; Cukierman, A.; Delabrouille, J.; Dobbs, M.; Ducout, A.; Elleflot, T.; Fabbian, G.; Feng, C.; Feeney, S.; Gilbert, A.; Goeckner-Wald, N.; Halverson, N. W.; Hasegawa, M.; Hattori, K.; Hazumi, M.; Hill, C.; Holzapfel, W. L.; Hori, Y.; Inoue, Y.; Jaehnig, G. C.; Jaffe, A. H.; Jeong, O.; Katayama, N.; Kaufman, J.; Keating, B.; Kermish, Z.; Keskitalo, R.; Kisner, T.; Le Jeune, M.; Lee, A. T.; Leitch, E. M.; Leon, D.; Linder, E.; Matsuda, F.; Matsumura, T.; Miller, N. J.; Myers, M. J.; Navaroli, M.; Nishino, H.; Okamura, T.; Paar, H.; Peloton, J.; Poletti, D.; Puglisi, G.; Rebeiz, G.; Reichardt, C. L.; Richards, P. L.; Ross, C.; Rotermund, K. M.; Schenck, D. E.; Sherwin, B. D.; Siritanasak, P.; Smecher, G.; Stebor, N.; Steinbach, B.; Stompor, R.; Suzuki, A.; Tajima, O.; Takakura, S.; Tikhomirov, A.; Tomaru, T.; Whitehorn, N.; Wilson, B.; Yadav, A.; Zahn, O.

    2015-08-01

    Atmosphere is one of the most important noise sources for ground-based cosmic microwave background (CMB) experiments. By increasing optical loading on the detectors, it amplifies their effective noise, while its fluctuations introduce spatial and temporal correlations between detected signals. We present a physically motivated 3D-model of the atmosphere total intensity emission in the millimeter and sub-millimeter wavelengths. We derive a new analytical estimate for the correlation between detectors time-ordered data as a function of the instrument and survey design, as well as several atmospheric parameters such as wind, relative humidity, temperature and turbulence characteristics. Using an original numerical computation, we examine the effect of each physical parameter on the correlations in the time series of a given experiment. We then use a parametric-likelihood approach to validate the modeling and estimate atmosphere parameters from the polarbear-i project first season data set. We derive a new 1.0% upper limit on the linear polarization fraction of atmospheric emission. We also compare our results to previous studies and weather station measurements. The proposed model can be used for realistic simulations of future ground-based CMB observations.

  7. Improved Visualization of Vertebrate Nuclear Pore Complexes by Field Emission Scanning Electron Microscopy

    National Research Council Canada - National Science Library

    Shaulov, Lihi; Harel, Amnon

    2012-01-01

    Field emission scanning electron microscopy (FESEM) can provide high-resolution three-dimensional surface imaging of many biological structures, including nuclear envelopes and nuclear pore complexes (NPCs...

  8. Electron emission yield for low energy electrons: Monte Carlo simulation and experimental comparison for Al, Ag, and Si

    Science.gov (United States)

    Pierron, J.; Inguimbert, C.; Belhaj, M.; Gineste, T.; Puech, J.; Raine, M.

    2017-06-01

    The electron emission under electron impact between 10 eV and 2 keV is investigated with a Monte Carlo (MC) code in aluminum, silver, and silicon. The code is based on the complex dielectric function theory to describe the inelastic scattering and uses the Mott's model of partial waves to describe the elastic scattering. It takes into account both volume and surface plasmon excitations. The simulation results are compared with the experimental measurements of electron emission yields (EEY) and energy spectra of low energy electrons performed in ultrahigh vacuum on Ar-etched bulk samples. Our MC simulations at low energy are found to be in fairly good agreement with our experimental measurements. The peaks corresponding to the surface plasmon, the volume plasmon and its multiples and to the Auger transitions appear clearly on the energy loss spectra of aluminum, silver, and silicon. The simulated EEY are also in fairly good agreement with our measurements and with data from the literature. The EEY at normal incidence is studied for secondary and backscattered electrons. A focus is made for the EEY below 50 eV where a fairly good agreement is found with Bronstein and Fraiman's measurements on vacuum evaporated samples. Below 2 keV, for silver and aluminum, the total EEY is given for different angles of incidence θ. Some discrepancies are observed between our experimental measurements and our MC simulations for high angles of incidence. These discrepancies can be attributed to the modeling of surface plasmon excitations, surface oxidation, or roughness that occur during the Ar-etching process.

  9. Observations of volcanic emissions using satellite remote sensing

    Science.gov (United States)

    Thomas, Helen E.

    Volcanoes pose a threat to the human population at regional and global scales and so efficient monitoring is essential in order to effectively manage and mitigate the risks that they pose. Volcano monitoring from space has been possible for over thirty years and now, more than ever, a suite of instruments exists with the capability to observe emissions of gas and ash from a unique perspective. The goal of this research is to demonstrate the use of a range of satellite-based sensors in order to detect and quantify volcanic sulphur dioxide, and to assess the relative performances of each sensor against one another. Such comparisons are important in order to standardise retrievals and permit better estimations of the global contribution of sulphur dioxide to the atmosphere from volcanoes for climate modelling. In this work, retrievals of volcanic sulphur dioxide from a number of instruments are compared, and the individual performances at quantifying emissions from large, explosive volcanic eruptions are assessed. Retrievals vary widely from sensor to sensor, and often the use of a number of sensors in synergy can provide the most complete picture, rather than just one instrument alone. Volcanic emissions have the ability to result significant economic loses by grounding aircraft due to the high risk associated with ash encountering aircraft. As sulphur dioxide is often easier to measure than ash, it is often used as a proxy. This work examines whether this is a reasonable assumption, using the Icelandic eruption in early 2010 as a case study. Results indicate that although the two species are for the most part collocated, separation can occur under some conditions, meaning that it is essential to accurately measure both species in order to provide effective hazard mitigation. Finally, the usefulness of satellite remote sensing in quantifying the passive degassing from Turrialba, Costa Rica is demonstrated. The increase in activity from 2005 - 2010 can be observed in

  10. A line-of-sight electron cyclotron emission receiver for electron cyclotron resonance heating feedback control of tearing modes

    DEFF Research Database (Denmark)

    Oosterbeek, J.W.; Bürger, A.; Westerhof, E.

    2008-01-01

    An electron cyclotron emission (ECE) receiver inside the electron cyclotron resonance heating (ECRH) transmission line has been brought into operation. The ECE is extracted by placing a quartz plate acting as a Fabry-Perot interferometer under an angle inside the electron cyclotron wave (ECW) beam...

  11. The role of electron induced secondary electron emission from SiO2 surfaces in capacitively coupled radio frequency plasmas operated at low pressures

    Science.gov (United States)

    Horváth, B.; Daksha, M.; Korolov, I.; Derzsi, A.; Schulze, J.

    2017-12-01

    The effects of electron induced secondary electron (SE) emission from SiO2 electrodes in single-frequency capacitively coupled plasmas (CCPs) are studied by particle-in-cell/Monte Carlo collisions (PIC/MCC) simulations in argon gas at 0.5 Pa for different voltage amplitudes. Unlike conventional simulations, we use a realistic model for the description of electron-surface interactions, which takes into account the elastic reflection and the inelastic backscattering of electrons, as well as the emission of electron induced SEs (δ-electrons). The emission coefficients corresponding to these elementary processes are determined as a function of the electron energy and angle of incidence, taking the properties of the surface into account. Compared to the results obtained by using a simplified model for the electron-surface interaction, widely used in PIC/MCC simulations of CCPs, which includes only elastic electron reflection at a constant probability of 0.2, strongly different electron power absorption and ionization dynamics are observed. We find that ion induced SEs (γ-electrons) emitted at one electrode and accelerated to high energies by the local sheath electric field propagate through the plasma almost collisionlessly and impinge on the opposing sheath within a few nanoseconds. Depending on the instantaneous local sheath voltage these energetic electrons are either reflected by the sheath electric field or they hit the electrode surface, where each γ-electron can generate multiple δ-electrons upon impact. These electron induced SEs are accelerated back into the plasma by the momentary sheath electric field and can again generate δ-electrons at the opposite electrode after propagating through the plasma bulk. Overall, a complex dynamics of γ- and δ-electrons is observed including multiple reflections between the boundary sheaths. At high voltages, the electron induced SE emission is found to strongly affect the plasma density and the ionization dynamics and

  12. Comparison of observed and theoretical Fe L emission from CIE plasmas

    Energy Technology Data Exchange (ETDEWEB)

    Carpenter, M; Beiersdorfer, P; Brown, G V; Chen, H C; Gu, M F; Jernigan, J G

    2007-11-08

    We analyze data from the Lawrence Livermore National Lab (LLNL) Electron Beam Ion Trap (EBIT) that simulates a CIE plasma by sweeping the electron beam to approximate a Maxwellian velocity distribution. These results are compared to spectra of confirmed astronomical CIE plasmas (e.g. outer regions of x-ray clusters) observed by XMM/RGS. We utilize the Photon Clean Method (PCM) to quantify these spectra (EBIT and XMM/RGS) in the form of ratios of Fe L lines in the emission complex near 1 keV. The variances of line fluxes are measured with bootstrap methods (Efron 1979). Both of these observations are further compared with theoretical predictions of Fe L line fluxes from APED and similar atomic databases.

  13. Conjugate Observations of EMIC Waves and Precipitation of Relativistic Electrons

    Science.gov (United States)

    Wang, Dedong; Shprits, Yuri; Yuan, Zhigang; Yu, Xiongdong; Huang, Shiyong

    2017-04-01

    Utilizing data from NOAA Geostationary Operational Environmental Satellite (GOES)-12 and low-altitude Polar Orbiting Environmental Satellites (POES)-15, a well-conjugate observation of Electromagnetic Ion Cyclotron (EMIC) waves and precipitation of ring current ions and relativistic electrons is reported. This event took place in periods without geomagnetic storms at near 21:30 on June 19, 2008. During this interval, GOES-12 observed EMIC waves at geosynchronous orbit in dusk Magnetic Local Time (MLT) sector. Conjugately, low-altitude NOAA POES-15 observed precipitation of ring current ions and relativistic electrons. To our knowledge, this is the best conjugated observation from satellites to illustrate EMIC wave-driven Relativistic Electron Precipitation (REP) in the MLT dusk sector during non-storm periods. The REP was observed by POES-15 at the same L (the radial distance in the equatorial plane under dipolar geomagnetic model) and MLT as where EMIC waves were observed by GOES-12, and the projections along the geomagnetic field line of NOAA GOES-12 and POES-15 at the altitude of 100 km above the Earth are nearly at the same geomagnetic latitude and longitude (△MLAT 0.7°, △MLong 0.6°). The diffusion coefficients of relativistic electrons by the EMIC waves are also calculated. This event suggests that, during the periods without geomagnetic storms, EMIC waves can also cause the loss of ring current ions and relativistic electrons through pitch-angle scattering in the dusk sector.

  14. Analysis and Modeling of Jovian Radio Emissions Observed by Galileo

    Science.gov (United States)

    Menietti, J. D.

    2003-01-01

    Our studies of Jovian radio emission have resulted in the publication of five papers in refereed journals, with three additional papers in progress. The topics of these papers include the study of narrow-band kilometric radio emission; the apparent control of radio emission by Callisto; quasi-periodic radio emission; hectometric attenuation lanes and their relationship to Io volcanic activity; and modeling of HOM attenuation lanes using ray tracing. A further study of the control of radio emission by Jovian satellites is currently in progress. Abstracts of each of these papers are contained in the Appendix. A list of the publication titles are also included.

  15. Spin-polarized free electron beam interaction with radiation and superradiant spin-flip radiative emission

    Directory of Open Access Journals (Sweden)

    A. Gover

    2006-06-01

    Full Text Available The problems of spin-polarized free-electron beam interaction with electromagnetic wave at electron-spin resonance conditions in a magnetic field and of superradiant spin-flip radiative emission are analyzed in the framework of a comprehensive classical model. The spontaneous emission of spin-flip radiation from electron beams is very weak. We show that the detectivity of electron spin resonant spin-flip and combined spin-flip/cyclotron-resonance-emission radiation can be substantially enhanced by operating with ultrashort spin-polarized electron beam bunches under conditions of superradiant (coherent emission. The proposed radiative spin-state modulation and the spin-flip radiative emission schemes can be used for control and noninvasive diagnostics of polarized electron/positron beams. Such schemes are of relevance in important scattering experiments off nucleons in nuclear physics and off magnetic targets in condensed matter physics.

  16. "Feathered" fractal surfaces to minimize secondary electron emission for a wide range of incident angles

    Science.gov (United States)

    Swanson, Charles; Kaganovich, Igor D.

    2017-07-01

    Complex structures on a material surface can significantly reduce the total secondary electron emission from that surface. The reduction occurs due to the capture of low-energy, true secondary electrons emitted at one point of the structure and intersecting another. We performed Monte Carlo calculations to demonstrate that fractal surfaces can reduce net secondary electron emission produced by the surface as compared to the flat surface. Specifically, we describe one surface, a "feathered" surface, which reduces the secondary electron emission yield more effectively than other previously considered configurations. Specifically, feathers grown onto a surface suppress secondary electron emission from shallow angles of incidence more effectively than velvet. We find that, for the surface simulated, secondary electron emission yield remains below 20% of its un-suppressed value, even for shallow incident angles, where the velvet-only surface gives reduction factor of only 50%.

  17. Kinetics of ion and prompt electron emission from laser-produced plasma

    Science.gov (United States)

    Farid, N.; Harilal, S. S.; Ding, H.; Hassanein, A.

    2013-07-01

    We investigated ion emission dynamics of laser-produced plasma from several elements, comprised of metals and non-metals (C, Al, Si, Cu, Mo, Ta, W), under vacuum conditions using a Faraday cup. The estimated ion flux for various targets studied showed a decreasing tendency with increasing atomic mass. For metals, the ion flux is found to be a function of sublimation energy. A comparison of temporal ion profiles of various materials showed only high-Z elements exhibited multiple structures in the ion time of flight profile indicated by the observation of higher peak kinetic energies, which were absent for low-Z element targets. The slower ions were seen regardless of the atomic number of target material propagated with a kinetic energy of 1-5 keV, while the fast ions observed in high-Z materials possessed significantly higher energies. A systematic study of plasma properties employing fast photography, time, and space resolved optical emission spectroscopy, and electron analysis showed that there existed different mechanisms for generating ions in laser ablation plumes. The origin of high kinetic energy ions is related to prompt electron emission from high-Z targets.

  18. Kinetics of ion and prompt electron emission from laser-produced plasma

    Energy Technology Data Exchange (ETDEWEB)

    Farid, N. [Center for Materials Under Extreme Environment, School of Nuclear Engineering, Purdue University, West Lafayette, Indiana 47907 (United States); Key Laboratory of Materials Modification by Laser, Ion and Electron Beams, School of Physics and Optical Engineering, Dalian University of Technology, Dalian (China); Harilal, S. S.; Hassanein, A. [Center for Materials Under Extreme Environment, School of Nuclear Engineering, Purdue University, West Lafayette, Indiana 47907 (United States); Ding, H. [Key Laboratory of Materials Modification by Laser, Ion and Electron Beams, School of Physics and Optical Engineering, Dalian University of Technology, Dalian (China)

    2013-07-15

    We investigated ion emission dynamics of laser-produced plasma from several elements, comprised of metals and non-metals (C, Al, Si, Cu, Mo, Ta, W), under vacuum conditions using a Faraday cup. The estimated ion flux for various targets studied showed a decreasing tendency with increasing atomic mass. For metals, the ion flux is found to be a function of sublimation energy. A comparison of temporal ion profiles of various materials showed only high-Z elements exhibited multiple structures in the ion time of flight profile indicated by the observation of higher peak kinetic energies, which were absent for low-Z element targets. The slower ions were seen regardless of the atomic number of target material propagated with a kinetic energy of 1–5 keV, while the fast ions observed in high-Z materials possessed significantly higher energies. A systematic study of plasma properties employing fast photography, time, and space resolved optical emission spectroscopy, and electron analysis showed that there existed different mechanisms for generating ions in laser ablation plumes. The origin of high kinetic energy ions is related to prompt electron emission from high-Z targets.

  19. Observation and analysis of self-amplified spontaneous emission at the APS low-energy undulator test line

    CERN Document Server

    Arnold, N D; Banks, G; Bechtold, R; Beczek, K; Benson, C; Berg, S; Berg, W; Biedron, S G; Biggs, J A; Boerste, K; Borland, M; Bosek, M; Brzowski, W R; Budz, J; Carwardine, J A; Castro, P; Chae, Y C; Christensen, S; Clark, C; Conde, M; Crosbie, E A; Decker, G A; Dejus, Roger J; Deleon, H; Den Hartog, P K; Deriy, B N; Dohan, D; Dombrowski, P; Donkers, D; Doose, C L; Dortwegt, R J; Edwards, G A; Eidelman, Y; Erdmann, M J; Error, J J; Ferry, R; Flood, R; Forrestal, J; Freund, H; Friedsam, H; Gagliano, J; Gai, W; Galayda, J N; Gerig, R; Gilmore, R L; Gluskin, E; Goeppner, G A; Goetzen, J; Gold, C; Grelick, A E; Hahne, M W; Hanuska, S; Harkay, K C; Harris, G; Hillman, A L; Hogrefe, R; Hoyt, J; Huang, Z; Jagger, J M; Jansma, W G; Jaski, M; Jones, S J; Keane, R T; Kelly, A L; Keyser, C; Kim, K J; Kim, S H; Kirshenbaum, M; Klick, J H; Knoerzer, K; Knott, M; Koldenhoven, R J; Labuda, S; Laird, R; Lang, J; Lenkszus, F R; Lessner, E S; Lewellen, J W; Li, Y; Lill, R M; Lumpkin, Alex H; Makarov, O A; Markovich, G M; McDowell, M; McDowell, W P; McNamara, P E; Meier, T; Meyer, D; Michalek, W; Milton, S V; Moe, H; Moog, E; Morrison, L; Nassiri, A; Noonan, J R; Otto, R; Pace, J; Pasky, S J; Penicka, J M; Pietryla, A F; Pile, G; Pitts, C; Power, J; Powers, T; Putnam, C C; Puttkammer, A J; Reigle, D; Reigle, L; Ronzhin, D; Rotela, E R; Russell, E F; Sajaev, Vadim; Sarkar, S; Scapino, J C; Schröder, K; Seglem, R A; Sereno, N S; Sharma, S K; Sidarous, J F; Singh, O; Smith, T L; Soliday, R; Sprau, G A; Stein, S J; Stejskal, B; Svirtun, V; Teng, L C; Theres, E; Thompson, K; Tieman, B J; Torres, J A; Trakhtenberg, E; Travish, G; Trento, G F; Vacca, J; Vasserman, I B; Vinokurov, N A; Walters, D R; Wang, J; Wang, X J; Warren, J; Wesling, S; Weyer, D L; Wiemerslage, G; Wilhelmi, K; Wright, R; Wyncott, D; Xu, S; Yang, B X; Yoder, W; Zabel, R B

    2001-01-01

    Exponential growth of self-amplified spontaneous emission at 530 nm was first experimentally observed at the Advanced Photon Source low-energy undulator test line in December 1999. Since then, further detailed measurements and analysis of the results have been made. Here, we present the measurements and compare these with calculations based on measured electron beam properties and theoretical expectations.

  20. Observations of Coastal IO Emissions on the Southern Hemisphere and Emission Potential of Different Seaweed Species

    Science.gov (United States)

    Horbanski, Martin; Schmitt, Stefan; Frieß, Udo; Pöhler, Denis; Johnston, Paul; Kreher, Karin; Robinson, Andrew D.; Thomas, Alan; Harris, Neil R. P.; Platt, Ulrich

    2014-05-01

    At coastal sites reactive iodine species emitted by seaweed in the intertidal zone during low tide are known to have an important influence on the atmospheric chemistry. However, many underlying mechanisms are presently not understood. Also coastal studies were focused on a few locations on the northern hemisphere and their predominant seaweed species laminaria digitata and ascophyllum nodosum. Therefore the spatial emission and extent of the areas where halogen chemistry is of importance needs to be much better quantified. Especially in the mid latitudes of the southern hemisphere RHS measurements are very sparse. Here we report the first observations of coastal iodine monoxide (IO) in the southern hemisphere during the HALMA/MAORI campaign which was carried out in February to March 2013 on the east coast of New Zealand's South Island at Shag Point located north of Dunedin. To detect IO we used a mobile Open Light Path Cavity Enhanced Differential Optical Absorption Spectroscopy (CE-DOAS) instrument and a stationary Long Path (LP)-DOAS Instrument, which was furthermore used to measure BrO, O3 and I2. The measurement path was positioned over the water and mainly measured air masses that only passes over submerged seaweed forests. With the CE-DOAS placed close to exposed seaweed patches (mainly Macrocystis Pyrifera) we were able to observe high IO mixing ratios of up to 50 ppt (2ppt detection limit). However, the LP-DOAS did not detect IO above the detection limit of 0.7 ppt. This is consistent with previous observations which found that seaweed only emits halogens when exposed to air. To further investigate the emission potential of the seaweed species we setup a Teflon chamber around the CE-DOAS and measured the emissions of five different species for several hours. Additionally the air in the chamber was probed by a compact gas chromatograph (μDIRAC) for measurements of halocarbons and a TEI Ozone monitor. We found very high IO mixing ratios of up to 500 ppt for

  1. Multispectral Observations of Explosive Gas Emissions from Santiaguito, Guatemala

    Science.gov (United States)

    Carn, S. A.; Watson, M.; Thomas, H.; Rodriguez, L. A.; Campion, R.; Prata, F. J.

    2016-12-01

    Santiaguito volcano, Guatemala, has been persistently active for decades, producing frequent explosions from its actively growing lava dome. Repeated release of volcanic gases contains information about conduit processes during the cyclical explosions at Santiaguito, but the composition of the gas phase and the amount of volatiles released in each explosion remains poorly constrained. In addition to its persistent activity, Santiaguito offers an exceptional opportunity to investigate lava dome degassing processes since the upper surface of the active lava dome can be viewed from the summit of neighboring Santa Maria. In January 2016 we conducted multi-spectral observations of Santiaguito's explosive eruption plumes and passive degassing from multiple perspectives as part of the first NSF-sponsored `Workshop on Volcanoes' instrument deployment. Gas measurements included open-path Fourier-Transform infrared (OP-FTIR) spectroscopy from the Santa Maria summit, coincident with ultraviolet (UV) and infrared (IR) camera and UV Differential Optical Absorption Spectroscopy (DOAS) from the El Mirador site below Santiaguito's active Caliente lava dome. Using the OP-FTIR in passive mode with the Caliente lava dome as the source of IR radiation, we were able to collect IR spectra at high temporal resolution prior to and during two explosions of Santiaguito on 7-8 January, with volcanic SO2 and H2O emissions detected. UV and IR camera data provide constraints on the total SO2 burden in the emissions (and potentially the volcanic ash burden), which coupled with the FTIR gas ratios provides new constraints on the mass and composition of volatiles driving explosions at Santiaguito. All gas measurements indicate significant volatile release during explosions with limited degassing during repose periods. In this presentation we will present ongoing analysis of the unique Santiaguito gas dataset including estimation of the total volatile mass released in explosions and an

  2. OBSERVATION OF HEATING BY FLARE-ACCELERATED ELECTRONS IN A SOLAR CORONAL MASS EJECTION

    Energy Technology Data Exchange (ETDEWEB)

    Glesener, Lindsay; Bain, Hazel M. [Space Sciences Laboratory, University of California at Berkeley, 7 Gauss Way, Berkeley, CA 94720 (United States); Krucker, Säm [Also at Institute of 4-D Technologies, School of Engineering, University of Applied Sciences Northwestern Switzerland, 5210 Windisch, Switzerland. (Switzerland); Lin, Robert P., E-mail: glesener@ssl.berkeley.edu [Also at Physics Department, University of California at Berkeley, Berkeley, CA 94720, USA. (United States)

    2013-12-20

    We report a Reuven Ramaty High Energy Solar Spectroscopic Imager (RHESSI) observation of flare-accelerated electrons in the core of a coronal mass ejection (CME) and examine their role in heating the CME. Previous CME observations have revealed remarkably high thermal energies that can far surpass the CME's kinetic energy. A joint observation by RHESSI and the Atmospheric Imaging Assembly of a partly occulted flare on 2010 November 3 allows us to test the hypothesis that this excess energy is collisionally deposited by flare-accelerated electrons. Extreme ultraviolet (EUV) images show an ejection forming the CME core and sheath, with isothermal multifilter analysis revealing temperatures of ∼11 MK in the core. RHESSI images reveal a large (∼100 × 50 arcsec{sup 2}) hard X-ray (HXR) source matching the location, shape, and evolution of the EUV plasma, indicating that the emerging CME is filled with flare-accelerated electrons. The time derivative of the EUV emission matches the HXR light curve (similar to the Neupert effect observed in soft and HXR time profiles), directly linking the CME temperature increase with the nonthermal electron energy loss, while HXR spectroscopy demonstrates that the nonthermal electrons contain enough energy to heat the CME. This is the most direct observation to date of flare-accelerated electrons heating a CME, emphasizing the close relationship of the two in solar eruptive events.

  3. Source location of chorus emissions observed by Cluster

    Directory of Open Access Journals (Sweden)

    M. Parrot

    Full Text Available One of the objectives of the Cluster mission is to study sources of various electromagnetic waves using the four satellites. This paper describes the methods we have applied to data recorded from the STAFF spectrum analyser. This instrument provides the cross spectral matrix of three magnetic and two electric field components. This spectral matrix is analysed to determine, for each satellite, the direction of the wave normal relative to the Earth’s magnetic field as a function of frequency and of time. Due to the Cluster orbit, chorus emissions are often observed close to perigee, and the data analysis determines the direction of these waves. Three events observed during different levels of magnetic activity are reported. It is shown that the component of the Poynting vector parallel to the magnetic field changes its sense when the satellites cross the magnetic equator, which indicates that the chorus waves propagate away from the equator. Detailed analysis indicates that the source is located in close vicinity of the plane of the geomagnetic equator.

    Key words. Magnetospheric physics (plasma waves and instabilities; storms and substorms; Space plasma physics (waves and instabilities

  4. First Optical Observations of Interhemispheric Electron Reflections Within Pulsating Aurora

    Science.gov (United States)

    Samara, M.; Michell, R. G.; Khazanov, G. V.

    2017-01-01

    A case study of a pulsating auroral event imaged optically at high time resolution presents direct observational evidence in agreement with the interhemispheric electron bouncing predicted by the Super Thermal Electron Transport model. Pulsation-on times are identified and subsequent equally spaced fainter pulsations are also noted and can be explained by a portion/percentage of the primary precipitating electrons reflecting upward from the ionosphere, traveling to the opposite hemisphere and reflecting upward again. The high time resolution of these data, combined with the short duration of the pulsation-on time (approx. 1 s) and the relatively long spacing between pulsations (approx. 6 to 9 s) made it possible to observe the faint optical pulses caused by the reflected electrons coming from the opposite hemisphere.

  5. Measurements of fast electron beams and soft X-ray emission from plasma-focus experiments

    Directory of Open Access Journals (Sweden)

    Surała Władysław

    2016-06-01

    Full Text Available The paper reports results of the recent experimental studies of pulsed electron beams and soft X-rays in plasma-focus (PF experiments carried out within a modified PF-360U facility at the NCBJ, Poland. Particular attention was focused on time-resolved measurements of the fast electron beams by means of two different magnetic analyzers, which could record electrons of energy ranging from about 41 keV to about 715 keV in several (6 or 8 measuring channels. For discharges performed with the pure deuterium filling, many strong electron signals were recorded in all the measuring channels. Those signals were well correlated with the first hard X-ray pulse detected by an external scintillation neutron-counter. In some of the analyzer channels, electron spikes (lasting about dozens of nanoseconds and appearing in different instants after the current peculiarity (so-called current dip were also recorded. For several discharges, fast ion beams, which were emitted along the z-axis and recorded with nuclear track detectors, were also investigated. Those measurements confirmed a multibeam character of the ion emission. The time-integrated soft X-ray images, which were taken side-on by means of a pinhole camera and sensitive X-ray films, showed the appearance of some filamentary structures and so-called hot spots. The application of small amounts of admixtures of different heavy noble gases, i.e. of argon (4.8% volumetric, krypton (1.6% volumetric, or xenon (0.8% volumetric, decreased intensity of the recorded electron beams, but increased intensity of the soft X-ray emission and showed more distinct and numerous hot spots. The recorded electron spikes have been explained as signals produced by quasi-mono-energetic microbeams emitted from tiny sources (probably plasma diodes, which can be formed near the observed hot spots.

  6. Understanding the bursty electron cyclotron emission during a sawtooth crash in the HT-7 tokamak

    Energy Technology Data Exchange (ETDEWEB)

    Li, Erzhong, E-mail: rzhonglee@ipp.ac.cn; Hu, Liqun; Chen, Kaiyun [Institute of Plasma Physics, Chinese Academy of Science, Hefei 230031 (China)

    2014-01-15

    Bursts in electron cyclotron emission (ECE) were observed during sawtooth crashes in HT-7 in discharges with ion cyclotron resonance heating injected near the q = 1 rational surface (q is the safety factor). The local ECE measurement indicated that the bursty radiation is only observed on channels near but a little away outward from the q = 1 magnetic surface. In conjunction with the soft x-ray tomography analysis, it was determined that, for the first time, only a compression process survives in the later stage of fast magnetic reconnection but before prompt heat transport. The compression enhanced the electron radiation temperature, the increased amplitude of which agreed well with the estimation according to a kinetic compression theory model [R. J. Hastie and T. C. Hender, Nucl. Fusion 28, 585 (1988)]. This paper presents the experimental evidence that there indeed exists a transient compression phase which results in the bursty ECE radiation during a sawtooth crash.

  7. Understanding the bursty electron cyclotron emission during a sawtooth crash in the HT-7 tokamak

    Science.gov (United States)

    Li, Erzhong; Hu, Liqun; Chen, Kaiyun

    2014-01-01

    Bursts in electron cyclotron emission (ECE) were observed during sawtooth crashes in HT-7 in discharges with ion cyclotron resonance heating injected near the q = 1 rational surface (q is the safety factor). The local ECE measurement indicated that the bursty radiation is only observed on channels near but a little away outward from the q = 1 magnetic surface. In conjunction with the soft x-ray tomography analysis, it was determined that, for the first time, only a compression process survives in the later stage of fast magnetic reconnection but before prompt heat transport. The compression enhanced the electron radiation temperature, the increased amplitude of which agreed well with the estimation according to a kinetic compression theory model [R. J. Hastie and T. C. Hender, Nucl. Fusion 28, 585 (1988)]. This paper presents the experimental evidence that there indeed exists a transient compression phase which results in the bursty ECE radiation during a sawtooth crash.

  8. Femtosecond photoelectron imaging of transient electronic states and Rydberg atom emission from electronically excited he droplets.

    Science.gov (United States)

    Kornilov, Oleg; Bünermann, Oliver; Haxton, Daniel J; Leone, Stephen R; Neumark, Daniel M; Gessner, Oliver

    2011-07-14

    Ultrafast relaxation of electronically excited pure He droplets is investigated by femtosecond time-resolved photoelectron imaging. Droplets are excited by extreme ultraviolet (EUV) pulses with photon energies below 24 eV. Excited states and relaxation products are probed by ionization with an infrared (IR) pulse with 1.6 eV photon energy. An initially excited droplet state decays on a time scale of 220 fs, leading predominantly to the emission of unaligned 1s3d Rydberg atoms. In a second relaxation channel, electronically aligned 1s4p Rydberg atoms are emitted from the droplet within less than 120 fs. The experimental results are described within a model that approximates electronically excited droplet states by localized, atomic Rydberg states perturbed by the local droplet environment in which the atom is embedded. The model suggests that, below 24 eV, EUV excitation preferentially leads to states that are localized in the surface region of the droplet. Electronically aligned 1s4p Rydberg atoms are expected to originate from excitations in the outermost surface regions, while nonaligned 1s3d Rydberg atoms emerge from a deeper surface region with higher local densities. The model is used to simulate the He droplet EUV absorption spectrum in good agreement with previously reported fluorescence excitation measurements.

  9. Polar cap electron densities from DE 1 plasma wave observations

    Science.gov (United States)

    Persoon, A. M.; Gurnett, D. A.; Shawhan, S. D.

    1983-01-01

    Electric-field-spectum measurements from the plasma-wave instrument on the Dynamics Explorer 1 spacecraft are used to study the local electron density at high altitudes in the northern polar-cap region. The electron density is determined from the upper cutoff of whistler-mode radiation at the electron plasma frequency. Median density values over the polar cap at L greater than 10 are found to vary from 35.2 + or - 8.5 cu cm at 2.1 earth radii to 0.99 + or - 0.51 cu cm at 4.66 earth radii. The steady-state radial-outflow model is examined for consistency with the observed density profile. A power-law fit to the radial variation of the electron density yields an exponent of - 3.85 + or - 0.32, which for the radial-outflow model implies a flow velocity increasing nearly linearly with incresing radial distance. Comparison of the observed electron densities with theoretical polar-wind densities yields consistent results up to 2.8 earth radii. A comparison of the observed electron densities with low-altitude density profiles from the Alouette II and ISIS 1 spacecraft illustrates transitions in the slope of the profile at 1.16 earth radii and between 1.55 and 2.0 earth radii. The changes in the density profile suggest that changes occur in the basic radial-transport processes at these altitudes.

  10. Electron and photon emissions from gold nanoparticles irradiated by X-ray photons

    Energy Technology Data Exchange (ETDEWEB)

    Casta, R., E-mail: castaromain@gmail.com, E-mail: romain.casta@irsamc.ups-tlse.fr; Champeaux, J.-P.; Moretto-Capelle, P.; Sence, M.; Cafarelli, P. [Université de Toulouse, UPS, Laboratoire Collisions Agrégats Réactivité, IRSAMC, CNRS, UMR 5589 (France)

    2015-01-15

    In this paper, we develop a totally new probabilistic model for the electron and photon emission of gold nanoparticles irradiated by X-ray photons. This model allows direct applications to recent researches about the radiotherapy enhancement by gold nanoparticles in the context of cancer treatment. Our model uses, in a complete original way, simulated Auger cascade and stopping power to compute electron emission spectra, photon emission spectra and released energy inside the material of gold nanoparticles. It allows us to present new results about the electron and photon emission of gold nanoparticle irradiated by hard X-rays.

  11. The effects of incident electron current density and temperature on the total electron emission yield of polycrystalline CVD diamond

    Energy Technology Data Exchange (ETDEWEB)

    Belhaj, M; Tondu, T; Inguimbert, V [ONERA/DESP 2, Avenue Edouard Belin, 31400 Toulouse Cedex (France); Barroy, Pierre; Silva, Francois; Gicquel, Alix, E-mail: Mohamed.Belhaj@onera.f [LIMHP, Universite Paris 13, CNRS Institut Galilee, 99 Avenue Jean-Baptiste Clement, 93430 Villetaneuse (France)

    2010-04-07

    The effects of temperature and incident electron current density on the total electron emission yield (TEEY) of polycrystalline diamond deposited by the chemical vapour deposition technique (CVD) were investigated at low electron beam fluence. It was found that the TEEY reversibly increases with the temperature and reversibly decreases with the current density. This behaviour is explained on the basis of a dynamic competition between the accumulation of holes (positive space charge), which internally reduces the secondary electron emission, and the thermally activated conductivity that tends to reduce the space charge formation.

  12. Fermi LAT observation of quiet gamma-ray emission from the Sun and first solar flares detection

    Energy Technology Data Exchange (ETDEWEB)

    Giglietto, N., E-mail: nicola.giglietto@ba.infn.it [Dipartimento Interateneo di Fisica Michelangelo Merlin dell' Universita degli Studi e del Politecnico di Bari, and INFN Sezione di Bari, Via Amendola 173, I-70126 Bari (Italy); Allafort, A. [SLAC (United States); Brigida, M. [Dipartimento Interateneo di Fisica Michelangelo Merlin dell' Universita degli Studi e del Politecnico di Bari, and INFN Sezione di Bari, Via Amendola 173, I-70126 Bari (Italy); Longo, F. [University of Trieste and INFN Sezione di Trieste (Italy); Omodei, N. [Stanford University (United States); Takahashi, H. [Hiroshima University (Japan); Tanaka, Y. [ISAS/JAXA (Japan)

    2012-11-11

    We show the latest results of Fermi-LAT observations of the quiescent Sun during the first 18 months of the mission. During this period the solar activity was at its minimum, hence the solar emission induced by cosmic rays was at its maximum. Two emission components are clearly distinguished: the point-like emission from the solar disk due to the cosmic-ray cascades in the solar atmosphere, and the extended emission due to inverse Compton scattering of cosmic ray electrons on solar photons in the heliosphere. We present the entire analysis, showing spectra and angular profiles of both components and discuss the comparison with models and future plans. Finally we report on Fermi Large Area Telescope (LAT) detection of the first solar flares and discussing the possible emission mechanisms.

  13. Identifying the 630 nm auroral arc emission height: A comparison of the triangulation, FAC profile, and electron density methods

    Science.gov (United States)

    Megan Gillies, D.; Knudsen, D.; Donovan, E.; Jackel, B.; Gillies, R.; Spanswick, E.

    2017-08-01

    We present a comprehensive survey of 630 nm (red-line) emission discrete auroral arcs using the newly deployed Redline Emission Geospace Observatory. In this study we discuss the need for observations of 630 nm aurora and issues with the large-altitude range of the red-line aurora. We compare field-aligned currents (FACs) measured by the Swarm constellation of satellites with the location of 10 red-line (630 nm) auroral arcs observed by all-sky imagers (ASIs) and find that a characteristic emission height of 200 km applied to the ASI maps gives optimal agreement between the two observations. We also compare the new FAC method against the traditional triangulation method using pairs of all-sky imagers (ASIs), and against electron density profiles obtained from the Resolute Bay Incoherent Scatter Radar-Canadian radar, both of which are consistent with a characteristic emission height of 200 km.

  14. Thirty per cent contrast in secondary-electron imaging by scanning field-emission microscopy.

    Science.gov (United States)

    Zanin, D A; De Pietro, L G; Peter, Q; Kostanyan, A; Cabrera, H; Vindigni, A; Bähler, Th; Pescia, D; Ramsperger, U

    2016-11-01

    We perform scanning tunnelling microscopy (STM) in a regime where primary electrons are field-emitted from the tip and excite secondary electrons out of the target-the scanning field-emission microscopy regime (SFM). In the SFM mode, a secondary-electron contrast as high as 30% is observed when imaging a monoatomic step between a clean W(110)- and an Fe-covered W(110)-terrace. This is a figure of contrast comparable to STM. The apparent width of the monoatomic step attains the 1 nm mark, i.e. it is only marginally worse than the corresponding width observed in STM. The origin of the unexpected strong contrast in SFM is the material dependence of the secondary-electron yield and not the dependence of the transported current on the tip-target distance, typical of STM: accordingly, we expect that a technology combining STM and SFM will highlight complementary aspects of a surface while simultaneously making electrons, selected with nanometre spatial precision, available to a macroscopic environment for further processing.

  15. Secondary electron emission characteristics of ion-textured copper and high-purity isotropic graphite surfaces

    Science.gov (United States)

    Curren, A. N.; Jensen, K. A.

    1984-01-01

    Experimentally determined values of true secondary electron emission and relative values of reflected primary electron yield for untreated and ion textured oxygen free high conductivity copper and untreated and ion textured high purity isotropic graphite surfaces are presented for a range of primary electron beam energies and beam impingement angles. This investigation was conducted to provide information that would improve the efficiency of multistage depressed collectors (MDC's) for microwave amplifier traveling wave tubes in space communications and aircraft applications. For high efficiency, MDC electrode surfaces must have low secondary electron emission characteristics. Although copper is a commonly used material for MDC electrodes, it exhibits relatively high levels of secondary electron emission if its surface is not treated for emission control. Recent studies demonstrated that high purity isotropic graphite is a promising material for MDC electrodes, particularly with ion textured surfaces. The materials were tested at primary electron beam energies of 200 to 2000 eV and at direct (0 deg) to near grazing (85 deg) beam impingement angles. True secondary electron emission and relative reflected primary electron yield characteristics of the ion textured surfaces were compared with each other and with those of untreated surfaces of the same materials. Both the untreated and ion textured graphite surfaces and the ion treated copper surface exhibited sharply reduced secondary electron emission characteristics relative to those of untreated copper. The ion treated graphite surface yielded the lowest emission levels.

  16. Onion-shell model for cosmic ray electrons and radio synchrotron emission in supernova remnants

    Science.gov (United States)

    Beck, R.; Drury, L. O.; Voelk, H. J.; Bogdan, T. J.

    1985-01-01

    The spectrum of cosmic ray electrons, accelerated in the shock front of a supernova remnant (SNR), is calculated in the test-particle approximation using an onion-shell model. Particle diffusion within the evolving remnant is explicity taken into account. The particle spectrum becomes steeper with increasing radius as well as SNR age. Simple models of the magnetic field distribution allow a prediction of the intensity and spectrum of radio synchrotron emission and their radial variation. The agreement with existing observations is satisfactory in several SNR's but fails in other cases. Radiative cooling may be an important effect, especially in SNR's exploding in a dense interstellar medium.

  17. Characterization of individual threading dislocations in GaN using ballistic electron emission microscopy.

    Science.gov (United States)

    Im, H J; Ding, Y; Pelz, J P; Heying, B; Speck, J S

    2001-09-03

    Threading dislocations (TDs) of molecular beam epitaxy grown GaN film were studied with ultrahigh vacuum ballistic electron emission microscopy in order to quantify any fixed negative charge at identifiable TDs, with approximately 3 nm spatial and approximately 10 meV local barrier resolution. In contrast to several prior studies, we find no indication of fixed negative dislocation charge at specific TD structures, with a conservative upper limit of approximately 0.25 e(-) per c-axis unit cell. We do observe evidence of positive surface charge at TDs and at GaN step edges, which may be due to local piezoelectric fields.

  18. Electron emission yields from boron-like Ar ions impinging on Au(1 0 0)

    Energy Technology Data Exchange (ETDEWEB)

    Bodewits, E., E-mail: ebodewits@kvi.nl [KVI - Atomic and Molecular Physics, University of Groningen, Zernikelaan 25, 9747 AA Groningen (Netherlands); Bekker, H.; Nijs, A.J. de [KVI - Atomic and Molecular Physics, University of Groningen, Zernikelaan 25, 9747 AA Groningen (Netherlands); Hoekstra, R., E-mail: hoekstra@kvi.nl [KVI - Atomic and Molecular Physics, University of Groningen, Zernikelaan 25, 9747 AA Groningen (Netherlands); Winklehner, D.; Daniel, B.; Kowarik, G.; Dobes, K.; Aumayr, F. [Institute of Applied Physics, TU Wien - Vienna University of Technology, A-1040 Vienna (Austria)

    2011-06-01

    Using a new experimental station to be installed at the HITRAP facility at GSI we studied electron emission yields of Ar{sup 13+} ions impinging on a clean Au(1 0 0) surface. By taking data under different incidence angles and at different initial kinetic energies, contributions from kinetic and potential electron emission are separated. The number distributions of the emitted electrons exhibit signatures of specific trajectory classes contributing differently to the electron emission yields. Support for the identification of the different trajectory classes is obtained from SRIM simulations.

  19. Electron emission from ferroelectric thin films enhanced by the presence of 90 degree ferroelectric domains.

    Science.gov (United States)

    Suchaneck, Gunnar; Vidyarthi, Vinay S; Gerlach, Gerald; Solnyshkin, Alexander V; Kislova, Inna L

    2007-12-01

    In this work, a ferroelectric domain-enhanced electron emission mechanism is proposed. The polarization distribution near 90 degrees domain walls is calculated by solving a set of second order differential equations, including the Poisson's one and equations derived from an expansion of the free energy Phi(P) in power series of the polarization according to the Devonshire-Landau-Ginzburg theory. Domain walls intersecting the emitting surface cause sufficient electric fields and lower the potential barrier for electron emission. This induces centers of enhanced electron emission. Relaxing domain walls were found to excite trapped excess electrons in front of the wall.

  20. Experimental Study of the Influence of Surface Conditions on Explosive Electron Emission From a Pin Cathode

    Science.gov (United States)

    Pikuz, S. A.; Shelkovenko, T. A.; Hammer, D. A.; Parkevich, E. V.; Tilikin, I. N.; Mingaleev, A. R.; Agafonov, A. V.

    2016-10-01

    Most theories of Explosive Electron Emission are based on the idea of cathode flares developing after explosion of metal whiskers on the cathode surface. The spatial structure of the flare, its origin and the process of flare development are still a matter of conjecture. In this work we used picosecond duration high resolution laser probing and X-pinch point-projection X-ray radiography to directly observe whisker explosion in a high-current diode. Pin cathodes made from thin 5-25 μm W, Cu or Mo wires were used as the load in return current circuits of hybrid X-pinches on the XP and BIN pulsers. Pin length, pin-anode gap and wire surface conditions were varied over a wide range. The diode current and voltage were measured. In experiments with small wire-anode gap (0.1 - 1 mm) development of the expanded dense core of the wire was observed except with lengths of 100-200 microns. Strong mitigation of the electron emission was observed in experiments with heated pins. Work at Cornell was supported by the NNSA Stewardship Sciences Academic Programs under DOE Cooperative Agreement No. DE-NA0001836. The work in Lebedev Institute was sponsored by the Russian Foundation for Basic Research Project No. 140201206.

  1. VLF emission triggering by a highly anisotropic energetic electron plasma

    Directory of Open Access Journals (Sweden)

    D. Nunn

    Full Text Available One of the objectives of the Cluster mission is to study sources of various electromagnetic waves using the four satellites. This paper describes the methods we have applied to data recorded from the STAFF spectrum analyser. This instrument provides the cross spectral matrix of three magnetic and two electric field components. This spectral matrix is analysed to determine, for each satellite, the direction of the wave normal relative to the Earth’s magnetic field as a function of frequency and of time. Due to the Cluster orbit, chorus emissions are often observed close to perigee, and the data analysis determines the direction of these waves. Three events observed during different levels of magnetic activity are reported. It is shown that the component of the Poynting vector parallel to the magnetic field changes its sense when the satellites cross the magnetic equator, which indicates that the chorus waves propagate away from the equator. Detailed analysis indicates that the source is located in close vicinity of the plane of the geomagnetic equator.

    Key words. Magnetospheric physics (plasma waves and instabilities; storms and substorms; Space plasma physics (waves and instabilities

  2. Temperature and energy effects on secondary electron emission from SiC ceramics induced by Xe17+ions.

    Science.gov (United States)

    Zeng, Lixia; Zhou, Xianming; Cheng, Rui; Wang, Xing; Ren, Jieru; Lei, Yu; Ma, Lidong; Zhao, Yongtao; Zhang, Xiaoan; Xu, Zhongfeng

    2017-07-25

    Secondary electron emission yield from the surface of SiC ceramics induced by Xe 17+ ions has been measured as a function of target temperature and incident energy. In the temperature range of 463-659 K, the total yield gradually decreases with increasing target temperature. The decrease is about 57% for 3.2 MeV Xe 17+ impact, and about 62% for 4.0 MeV Xe 17+ impact, which is much larger than the decrease observed previously for ion impact at low charged states. The yield dependence on the temperature is discussed in terms of work function, because both kinetic electron emission and potential electron emission are influenced by work function. In addition, our experimental data show that the total electron yield gradually increases with the kinetic energy of projectile, when the target is at a constant temperature higher than room temperature. This result can be explained by electronic stopping power which plays an important role in kinetic electron emission.

  3. Observation of suprathermal electrons during magnetic reconnection at the sawtooth instability in DIII-D TOKAMAK

    CERN Document Server

    Savrukhin, R V

    2002-01-01

    OAK A271 Observation of suprathermal electrons during magnetic reconnection at the sawtooth instability in DIII-D TOKAMAK. Intense bursts of x-ray and electron cyclotron emission are observed during sawtooth instabilities in high-temperature plasmas in the DIII-D tokamak. The bursts are initiated around the X-point of the m = 1, n = 1 magnetic island at the beginning of the sawtooth crash and are displaced to larger radii later during the temperature collapse. Reconstruction of the magnetic configuration using motional Stark effect (MSE) data and numerical simulations indicates that the bursts can be connected with suprathermal electrons (E sub r approx 30-40 keV) generated during reconnection of the magnetic field around the q = 1 surface.

  4. Cluster PEACE observations of electrons of spacecraft origin

    Directory of Open Access Journals (Sweden)

    S. Szita

    Full Text Available The two PEACE (Plasma Electron And Current Experiment sensors on board each Cluster spacecraft sample the electron velocity distribution across the full 4 solid angle and the energy range 0.7 eV to 26 keV with a time resolution of 4 s. We present high energy and angular resolution 3D observations of electrons of spacecraft origin in the various environments encountered by the Cluster constellation, including a lunar eclipse interval where the spacecraft potential was reduced but remained positive, and periods of ASPOC (Active Spacecraft POtential Control operation which reduced the spacecraft potential. We demonstrate how the spacecraft potential may be found from a gradient change in the PEACE low energy spectrum, and show how the observed spacecraft electrons are confined by the spacecraft potential. We identify an intense component of the spacecraft electrons with energies equivalent to the spacecraft potential, the arrival direction of which is seen to change when ASPOC is switched on. Another spacecraft electron component, observed in the sunward direction, is reduced in the eclipse but unaffected by ASPOC, and we believe this component is produced in the analyser by solar UV. We find that PEACE anodes with a look direction along the spacecraft surfaces are more susceptible to spacecraft electron contamination than those which look perpendicular to the surface, which justifies the decision to mount PEACE with its field-of-view radially outward rather than tangentially.

    Key words. Magnetosheric physics (general or miscellaneous Space plasma physics (spacecraft sheaths, wakes, charging

  5. Cluster PEACE observations of electrons of spacecraft origin

    Directory of Open Access Journals (Sweden)

    S. Szita

    2001-09-01

    Full Text Available The two PEACE (Plasma Electron And Current Experiment sensors on board each Cluster spacecraft sample the electron velocity distribution across the full 4 solid angle and the energy range 0.7 eV to 26 keV with a time resolution of 4 s. We present high energy and angular resolution 3D observations of electrons of spacecraft origin in the various environments encountered by the Cluster constellation, including a lunar eclipse interval where the spacecraft potential was reduced but remained positive, and periods of ASPOC (Active Spacecraft POtential Control operation which reduced the spacecraft potential. We demonstrate how the spacecraft potential may be found from a gradient change in the PEACE low energy spectrum, and show how the observed spacecraft electrons are confined by the spacecraft potential. We identify an intense component of the spacecraft electrons with energies equivalent to the spacecraft potential, the arrival direction of which is seen to change when ASPOC is switched on. Another spacecraft electron component, observed in the sunward direction, is reduced in the eclipse but unaffected by ASPOC, and we believe this component is produced in the analyser by solar UV. We find that PEACE anodes with a look direction along the spacecraft surfaces are more susceptible to spacecraft electron contamination than those which look perpendicular to the surface, which justifies the decision to mount PEACE with its field-of-view radially outward rather than tangentially.Key words. Magnetosheric physics (general or miscellaneous Space plasma physics (spacecraft sheaths, wakes, charging

  6. Interpretation of Midlatitude Observations of Total Electron Content

    Science.gov (United States)

    Ostrander, Graham; Bartels, Michael; Gallagher, Hugh

    2007-04-01

    In October 2004, a Coherent Ionospheric Doppler Receiver (CIDR) was installed at SUNY Oneonta. The CIDR measures Doppler shifts on 150 MHz and 400 MHz signals from beacons on a series of low earth orbiting satellites as these signals transect the ionosphere. The integrated number of electrons between the satellite and the receiver (known as the total electron content, TEC) is derived from the difference in the Doppler shifts of the 150 MHz and 400 MHz signals. Observations of TEC as a function of satellite elevation angle are fit to a model of the ionosphere to infer the ionospheric electron density. In order to assess the efficacy of this technique, our results are compared to observations from the array of North American GPS receivers. The technique is then used to examine the dependence of properties of the midlatitude density trough on magnetic activity.

  7. Structural preablation dynamics of graphite observed by ultrafast electron crystallography

    NARCIS (Netherlands)

    Carbone, Fabrizio; Baum, Peter; Rudolf, Petra; Zewail, Ahmed H.

    2008-01-01

    By means of time-resolved electron crystallography, we report direct observation of the structural dynamics of graphite, providing new insights into the processes involving coherent lattice motions and ultrafast graphene ablation. When graphite is excited by an ultrashort laser pulse, the excited

  8. Heating-induced variations of secondary electron emission from ion-cleaned copper samples.

    Science.gov (United States)

    Hu, Xiao-Chuan; Zhang, Hai-Bo; Cao, Meng; Zhang, Na; Cui, Wan-Zhao

    2014-09-01

    Secondary electron (SE) emission due to electron impact depends strongly on surface conditions. The variations of SE yield and spectrum with the heating temperature of Ar-ion-cleaned oxygen-free copper samples are therefore measured in situ in a multifunctional ultrahigh vacuum system. The SE yield and the SE spectrum are observed to increase and to narrow, respectively, after sample heating. The maximum SE yield increases from 0.97 before heating to 1.25 after heating at ∼313 °C, and the corresponding full width at half maximum of SE spectrum decreases considerably from 9.3 to 5.5 eV. More CO2 and Ar ions are shown to desorb at a higher heating temperature by residual gas analysis, indicating their contribution to the reduction in work function and surface potential barrier. Ar-ion desorption appears to affect the SE spectrum more than the SE yield. The obtained results provide a new insight into complicated surface influences on SE emission in thermal applications of scanning electron microscopy. Copyright © 2014 Elsevier Ltd. All rights reserved.

  9. Observation of very low frequency emissions at Indian Antarctic ...

    Indian Academy of Sciences (India)

    Recently, we have succeeded in recording VLF emissions at the Indian Antarctic station, Maitri (geom. lat. 62° S, geom. long. 57.23°E, =4.5) using a T-type antenna, pre/main amplifiers and digital audio tape recorder. VLF hiss in the frequency ranges 11–13 kHz and 13–14.5 kHz and some riser-type emissions in the ...

  10. Field emission scanning electron microscopy of biofilm-growing bacteria involved in nosocomial infections.

    Science.gov (United States)

    Vuotto, Claudia; Donelli, Gianfranco

    2014-01-01

    Scanning electron microscopy (SEM) provides useful information on the shape, size, and localization within the biofilm of single bacteria as well as on the steps of biofilm formation process, on bacterial interactions, and on production of extracellular polymeric substances.When biofilms are constituted by microbial species involved in health care-associated infections, information provided by SEM can be fruitfully used not only for basic researches but also for diagnostic purposes.The protocols currently used in our laboratory for biofilm investigation by SEM are reported here. Particularly, the procedures to fix, dehydrate, and metalize in vitro-developed biofilms or ex vivo clinical specimens colonized by biofilm-growing microorganisms are described as well as the advantages of the observation of these samples by field emission scanning electron microscopy.

  11. Observational study of generation conditions of substorm-associated low-frequency AKR emissions

    Directory of Open Access Journals (Sweden)

    A. Olsson

    2004-11-01

    Full Text Available It has lately been shown that low-frequency bursts of auroral kilometric radiation (AKR are nearly exclusively associated with substorm expansion phases. Here we study low-frequency AKR using Polar PWI and Interball POLRAD instruments to constrain its possible generation mechanisms. We find that there are more low-frequency AKR emission events during wintertime and equinoxes than during summertime. The dot-AKR emission radial distance range coincides well with the region where the deepest density cavities are seen statistically during Kp>2. We suggest that the dot-AKR emissions originate in the deepest density cavities during substorm onsets. The mechanism for generating dot-AKR is possibly strong Alfvén waves entering the cavity from the magnetosphere and changing their character to more inertial, which causes the Alfvén wave associated parallel electric field to increase. This field may locally accelerate electrons inside the cavity enough to produce low-frequency AKR emission. We use Interball IESP low-frequency wave data to verify that in about half of the cases the dot-AKR is accompanied by low-frequency wave activity containing a magnetic component, i.e. probably inertial Alfvén waves. Because of the observational geometry, this result is consistent with the idea that inertial Alfvén waves might always be present in the source region when dot-AKR is generated. The paper illustrates once more the importance of radio emissions as a powerful remote diagnostic tool of auroral processes, which is not only relevant for the Earth's magnetosphere but may be relevant in the future in studying extrasolar planets.

  12. Observational study of generation conditions of substorm-associated low-frequency AKR emissions

    Directory of Open Access Journals (Sweden)

    A. Olsson

    2004-11-01

    Full Text Available It has lately been shown that low-frequency bursts of auroral kilometric radiation (AKR are nearly exclusively associated with substorm expansion phases. Here we study low-frequency AKR using Polar PWI and Interball POLRAD instruments to constrain its possible generation mechanisms. We find that there are more low-frequency AKR emission events during wintertime and equinoxes than during summertime. The dot-AKR emission radial distance range coincides well with the region where the deepest density cavities are seen statistically during Kp>2. We suggest that the dot-AKR emissions originate in the deepest density cavities during substorm onsets. The mechanism for generating dot-AKR is possibly strong Alfvén waves entering the cavity from the magnetosphere and changing their character to more inertial, which causes the Alfvén wave associated parallel electric field to increase. This field may locally accelerate electrons inside the cavity enough to produce low-frequency AKR emission. We use Interball IESP low-frequency wave data to verify that in about half of the cases the dot-AKR is accompanied by low-frequency wave activity containing a magnetic component, i.e. probably inertial Alfvén waves. Because of the observational geometry, this result is consistent with the idea that inertial Alfvén waves might always be present in the source region when dot-AKR is generated. The paper illustrates once more the importance of radio emissions as a powerful remote diagnostic tool of auroral processes, which is not only relevant for the Earth's magnetosphere but may be relevant in the future in studying extrasolar planets.

  13. Electron holes observed in the Moon Plasma Wake

    Science.gov (United States)

    Hutchinson, I. H.; Malaspina, D.; Zhou, C.

    2017-10-01

    Electrostatic instabilities are predicted in the magnetized wake of plasma flowing past a non-magnetic absorbing object such as a probe or the moon. Analysis of the data from the Artemis satellites, now orbiting the moon at distances ten moon radii and less, shows very clear evidence of fast-moving isolated solitary potential structures causing bipolar electric field excursions as they pass the satellite's probes. These structures have all the hallmarks of electron holes: BGK solitons typically a few Debye-lengths in size, self-sustaining by a deficit of phase-space density on trapped orbits. Electron holes are now observed to be widespread in space plasmas. They have been observed in PIC simulations of the moon wake to be the non-linear consequence of the predicted electron instabilities. Simulations document hole prevalence, speed, length, and depth; and theory can explain many of these features from kinetic analysis. The solar wind wake is certainly the cause of the overwhelming majority of the holes observed by Artemis, because we observe almost all holes to be in or very near to the wake. We compare theory and simulation of the hole generation, lifetime, and transport mechanisms with observations. Work partially supported by NASA Grant NNX16AG82G.

  14. Modelling coronal electron density and temperature profiles based on solar magnetic field observations

    Science.gov (United States)

    Rodríguez Gómez, J. M.; Antunes Vieira, L. E.; Dal Lago, A.; Palacios, J.; Balmaceda, L. A.; Stekel, T.

    2017-10-01

    The density and temperature profiles in the solar corona are complex to describe, the observational diagnostics is not easy. Here we present a physics-based model to reconstruct the evolution of the electron density and temperature in the solar corona based on the configuration of the magnetic field imprinted on the solar surface. The structure of the coronal magnetic field is estimated from Potential Field Source Surface (PFSS) based on magnetic field from both observational synoptic charts and a magnetic flux transport model. We use an emission model based on the ionization equilibrium and coronal abundances from CHIANTI atomic database 8.0. The preliminary results are discussed in details.

  15. Method of synthesizing small-diameter carbon nanotubes with electron field emission properties

    Science.gov (United States)

    Liu, Jie (Inventor); Du, Chunsheng (Inventor); Qian, Cheng (Inventor); Gao, Bo (Inventor); Qiu, Qi (Inventor); Zhou, Otto Z. (Inventor)

    2009-01-01

    Carbon nanotube material having an outer diameter less than 10 nm and a number of walls less than ten are disclosed. Also disclosed are an electron field emission device including a substrate, an optionally layer of adhesion-promoting layer, and a layer of electron field emission material. The electron field emission material includes a carbon nanotube having a number of concentric graphene shells per tube of from two to ten, an outer diameter from 2 to 8 nm, and a nanotube length greater than 0.1 microns. One method to fabricate carbon nanotubes includes the steps of (a) producing a catalyst containing Fe and Mo supported on MgO powder, (b) using a mixture of hydrogen and carbon containing gas as precursors, and (c) heating the catalyst to a temperature above 950.degree. C. to produce a carbon nanotube. Another method of fabricating an electron field emission cathode includes the steps of (a) synthesizing electron field emission materials containing carbon nanotubes with a number of concentric graphene shells per tube from two to ten, an outer diameter of from 2 to 8 nm, and a length greater than 0.1 microns, (b) dispersing the electron field emission material in a suitable solvent, (c) depositing the electron field emission materials onto a substrate, and (d) annealing the substrate.

  16. Observation of Bacteriophage Ultrastructure by Cryo-electron Microscopy.

    Science.gov (United States)

    Cuervo, Ana; Carrascosa, José L

    2018-01-01

    Transmission Electron Microscopy (TEM) is an ideal method to observe and determine the structure of bacteriophages. From early studies by negative staining to the present atomic structure models derived from cryo-TEM, bacteriophage detection, classification, and structure determination has been mostly done by electron microscopy. Although embedding in metal salts has been a routine method for virus observation for many years, preservation of bacteriophages in a thin layer of fast frozen buffer has proven to be a most convenient preparation method for obtaining images using cryo-electron microscopy (cryo-EM). In this technique, frozen samples are observed at liquid nitrogen temperature and the images are acquired using different recording media. The incorporation of direct electron detectors has been a fundamental step to achieve atomic resolution images of a number of viruses. These projection images can be numerically combined using different approaches to render a three-dimensional model of the virus. For those viral components exhibiting any symmetry, averaging procedures help to render near-atomic resolution structures.

  17. Coherent Cerenkov emission from electrons streaming through a photonic crystal

    NARCIS (Netherlands)

    van der Slot, Petrus J.M.

    2014-01-01

    Cerenkov radiation is usually incoherent radiation emitted by charged particles when they pass through a medium with sufficiently high, usually relativistic velocity. It has recently been shown that in photonic crystals Cerenkov emission is possible without a velocity threshold, however emission

  18. Energetic electron fluxes at Saturn from Cassini observations

    Science.gov (United States)

    Tang, Rongxin; Summers, Danny

    2012-06-01

    Energetic electron fluxes (18 keV-21 MeV) observed by the MIMI/LEMMS instrument on the Cassini mission during 2004 to 2008 are analyzed. We consider all 101 orbits and we select portions of the orbits that lie within 0.5 RS of the magnetic equatorial plane, where RS is Saturn's radius. We determine the average electron differential flux and integral flux at specified L-shells in the range 4.5 Kennel-Petschek theory. We find that at lower L-shells, L Kennel-Petschek limit; and at larger L-shells, 7 Kennel-Petschek limit.

  19. Observations of Electron Vorticity in the Inner Plasma Sheet

    Science.gov (United States)

    Gurgiolo, C.; Goldstein, M. L.; Vinas, A. F.; Matthaeus, W. H.; Fazakerley, A. N.

    2011-01-01

    From a limited number of observations it appears that vorticity is a common feature in the inner plasma sheet. With the four Cluster spacecraft and the four PEACE instruments positioned in a tetrahedral configuration, for the first time it is possible to directly estimate the electron fluid vorticity in a space plasma. We show examples of electron fluid vorticity from multiple plasma sheet crossings. These include three time periods when Cluster passed through a reconnection ion diffusion region. Enhancements in vorticity are seen in association with each crossing of the ion diffusion region.

  20. Excitation threshold of Stimulated Electromagnetic Emissions SEEs generated at pump frequency near the third electron gyroharmonic

    Science.gov (United States)

    Mahmoudian, A.; Bernhardt, P. A.; Scales, W.

    2012-12-01

    The High-Frequency Active Auroral Research Program (HAARP) in Gakona, Alaska provides effective radiated powers in the megawatt range that have allowed researchers to study many non-linear effects of wave-plasma interactions. Stimulated Electromagnetic Emission (SEE) is of interest to the ionospheric community for its diagnostic purposes. In recent HAARP heating experiments, it has been shown that during the Magnetized Stimulated Brillouin Scattering MSBS instability, the pumped electromagnetic wave may decay into an electromagnetic wave and a low frequency electrostatic wave (either ion acoustic IA wave or electrostatic ion cyclotron EIC wave). Using Stimulated Electromagnetic Emission (SEE) spectral features, side bands which extend above and below the pump frequency can yield significant diagnostics for the modified ionosphere. It has been shown that the IA wave frequency offsets can be used to measure electron temperature in the heated ionosphere and EIC wave offsets can be used as a sensitive method to determine the ion species by measuring ion mass using the ion gyro-frequency offset. The threshold of each emission line has been measured by changing the amplitude of pump wave. The experimental results aimed to show the threshold for transmitter power to excite IA wave propagating along the magnetic field lines as well as for EIC wave excited at an oblique angle relative to the background magnetic field. Another parametric decay instability studied is the ion Bernstein decay instability that has been attributed to the simultaneous parametric decay of electron Bernstein waves into multiple electron Bernstein and ion Bernstein waves. The SIB process is thought to involve mode conversion from EM to EB waves followed by parametric decay of the EB wave to multiple EB and IB waves. The parametric decay instability of ion Bernstein modes has been observed simultaneously for the first time at the third electron gyroharmonics during 2011 Summer Student Research

  1. Motorcycles, mopeds: polluting emissions and energy consumption. Initial observations

    Energy Technology Data Exchange (ETDEWEB)

    Barbusse, St.

    2001-05-01

    The present French fleet of two-wheel vehicles is very heterogeneous (2- and 4-stroke engines with cubic capacity from 50 cm{sup 3} to 1300 cm{sup 3} and automatic or manual transmissions) and generally lacking in any anti-pollution system, which leads to high emission levels of carbon monoxide and unburned hydrocarbons. Mopeds have high emission levels compared to those of 4-wheel vehicles, which have decreased markedly since 1970. The following chart of limit values confirms that the gap between these two vehicle categories in polluting emissions has increased in just a few years. The implementation of more restrictive regulations about pollution emissions was delayed for a long time because of cumulative technological delays in comparison to private vehicles. But in the end a European directive differentiating two kinds of two-wheel vehicles: mopeds and motorcycles was voted in 1997 (no. 97/24). There are two stages (in 1999 and 2002 respectively) for lowering emissions levels for mopeds (engine size smaller than 50 cm{sup 3}). For motorcycles a single stage was set for 1999, with a second stage still under consideration. Given the high stakes in terms of decreased pollution emission rom the necessary technological leap for the shift from outmoded carburetor engines to more refined technology (injection + post-treatment) under ADEME's guidance, the issue of exhaust-pollution reduction of two-wheel vehicles was included in both the PRIMEQUAL programme, 'Automobile Pollution Emissions' and the PREDIT call for proposals, 'Cycle Fuel Engine Pollution Reduction' in 1999. Several projects of varying technical natures (evaluations of existing engines and technological studies of new solutions in engines and exhaust pollution reduction) have been implemented in partnership with specialist research laboratories (such as the IFP) and manufacturers and outfitters in the sector (Sagem, Arvin Exhaust, Peugeot Motorcycles). Moreover, as the principle

  2. Field emission from individual multiwalled carbon nanotubes prepared in an electron microscope

    NARCIS (Netherlands)

    de Jonge, N.; van Druten, N.J.

    2003-01-01

    Individual multiwalled carbon nanotube field emitters were prepared in a scanning electron microscope. The angular current density, energy spectra, and the emission stability of the field-emitted electrons were measured. An estimate of the electron source brightness was extracted from the

  3. LHR band emissions at mid-latitude and their relationship to ionospheric ELF hiss and relativistic electrons

    Directory of Open Access Journals (Sweden)

    A. Morioka

    2005-03-01

    Full Text Available LHR band emissions observed at mid-latitude were investigated using data from the EXOS-C (Ohzora satellite. A typical feature of the LHR band emissions is a continuous banded structure without burst-like and cut-off features whose center frequency decreases as the satellite moves to higher latitudes. A statistical analysis of the occurrence characteristics of the phenomena showed that mid-latitude LHR emissions are distributed inside the plasmapause during magnetically quiet periods, and the poleward boundary of the emission region moves to lower latitudes as the magnetic activity increases. The altitude distribution of the waves suggests that the propagation in the LHR duct formed horizontally in the mid-latitude upper-ionosphere. The emission is closely related to the occurrence of ionospheric ELF hiss. It is also shown that LHR emissions are commonly observed in the slot region of the radiation belt, and they sometimes accompany the enhancement of the ionospheric electron temperature. The generation of the LHR band emissions is discussed based on the observed characteristics.

  4. Fast emission estimates in China and South Africa constrained by satellite observations

    Science.gov (United States)

    Mijling, Bas; van der A, Ronald

    2013-04-01

    Emission inventories of air pollutants are crucial information for policy makers and form important input data for air quality models. Unfortunately, bottom-up emission inventories, compiled from large quantities of statistical data, are easily outdated for emerging economies such as China and South Africa, where rapid economic growth change emissions accordingly. Alternatively, top-down emission estimates from satellite observations of air constituents have important advantages of being spatial consistent, having high temporal resolution, and enabling emission updates shortly after the satellite data become available. However, constraining emissions from observations of concentrations is computationally challenging. Within the GlobEmission project (part of the Data User Element programme of ESA) a new algorithm has been developed, specifically designed for fast daily emission estimates of short-lived atmospheric species on a mesoscopic scale (0.25 × 0.25 degree) from satellite observations of column concentrations. The algorithm needs only one forward model run from a chemical transport model to calculate the sensitivity of concentration to emission, using trajectory analysis to account for transport away from the source. By using a Kalman filter in the inverse step, optimal use of the a priori knowledge and the newly observed data is made. We apply the algorithm for NOx emission estimates in East China and South Africa, using the CHIMERE chemical transport model together with tropospheric NO2 column retrievals of the OMI and GOME-2 satellite instruments. The observations are used to construct a monthly emission time series, which reveal important emission trends such as the emission reduction measures during the Beijing Olympic Games, and the impact and recovery from the global economic crisis. The algorithm is also able to detect emerging sources (e.g. new power plants) and improve emission information for areas where proxy data are not or badly known (e

  5. Increase of the performances of electron cyclotron resonance ion sources by using cold electron emission

    CERN Document Server

    Schaechter, I; Badescu-Singureanu, A I; Stiebing, K E; Runkel, S; Hohn, O; Schmidt, L; Schmidt-Böcking, H; Drentje, A; Rodríguez, G

    2003-01-01

    The possibility of a significant increase of the high charge state ion beams delivered by electron cyclotron resonance (ECR) ion sources was approached in IFIN-HH, Bucharest, Romania by a new method. It consists in the introduction in the plasma chamber of the ECR ion source of a metal-dielectric (MD) structure characterized by very high secondary electron emission properties. The intensities of argon ion beams extracted from the 14 GHz ECR ion sources of IKF, Frankfurt/Main, Germany and KVI, Groningen, Netherlands were measured both in the standard mode of operation of the sources and in the presence of a MD structure. Similar results were obtained in both experiments when the MD structure was used showing a net shift of the beam intensity towards higher charge states as compared with the usual standard plasma chamber of the ECR ion sources. Ion current enhancement factors of up to two orders of magnitude were obtained for Ar sup 1 sup 6 sup + ions. (authors)

  6. Electron transport in ultra-thin films and ballistic electron emission microscopy

    Science.gov (United States)

    Claveau, Y.; Di Matteo, S.; de Andres, P. L.; Flores, F.

    2017-03-01

    We have developed a calculation scheme for the elastic electron current in ultra-thin epitaxial heterostructures. Our model uses a Keldysh’s non-equilibrium Green’s function formalism and a layer-by-layer construction of the epitaxial film. Such an approach is appropriate to describe the current in a ballistic electron emission microscope (BEEM) where the metal base layer is ultra-thin and generalizes a previous one based on a decimation technique appropriated for thick slabs. This formalism allows a full quantum mechanical description of the transmission across the epitaxial heterostructure interface, including multiple scattering via the Dyson equation, which is deemed a crucial ingredient to describe interfaces of ultra-thin layers properly in the future. We introduce a theoretical formulation needed for ultra-thin layers and we compare with results obtained for thick Au(1 1 1) metal layers. An interesting effect takes place for a width of about ten layers: a BEEM current can propagate via the center of the reciprocal space (\\overlineΓ ) along the Au(1 1 1) direction. We associate this current to a coherent interference finite-width effect that cannot be found using a decimation technique. Finally, we have tested the validity of the handy semiclassical formalism to describe the BEEM current.

  7. Angular studies of potential electron emission in the interaction of slow ions with Al surfaces

    Science.gov (United States)

    Riccardi; Barone; Bonanno; Oliva; Baragiola

    2000-01-10

    We report energy distributions of electrons emitted from Al surfaces under impact by 1 keV Ar+ and 1-5 keV Ne+ ions. The variation of the energy distributions with the angle of incidence is different for both ions and provides information on the mechanism responsible for electron emission. For Ar+ electron emission results mainly from Auger neutralization, while for Ne+ an important emission mechanism is the decay of plasmon excitations. We find a transition between surface and bulk plasmon excitations as the energy of the ion is increased.

  8. POSSIBLE ORIGIN OF RADIO EMISSION FROM NONTHERMAL ELECTRONS IN HOT ACCRETION FLOWS FOR LOW-LUMINOSITY ACTIVE GALACTIC NUCLEI

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Hu; Wu, Qingwen, E-mail: qwwu@hust.edu.cn [School of Physics, Huazhong University of Science and Technology, Wuhan 430074 (China)

    2013-02-10

    The two components of radio emission, above and below 86 GHz, respectively, from the Galactic center source Sgr A* can be naturally explained by the hybrid of thermal and nonthermal electrons in hot accretion flows (e.g., radiatively inefficient accretion flow; RIAF). We further apply this model to a sample of nearby low-luminosity active galactic nuclei (LLAGNs), which are also believed to be powered by RIAF. We selected LLAGNs with only compact radio cores according to high-resolution radio observations, and sources observed with jets or jet-like features are excluded. We find that the radio emission of LLAGNs is severely underpredicted by the pure RIAF model, but can be naturally explained by the RIAF model with a hybrid electron population consisting of both thermal and nonthermal particles. Our model can roughly reproduce the observed anticorrelation between the mass-corrected radio loudness and Eddington ratio for the LLAGNs in our sample. We further model the spectral energy distributions of each source in our sample and find that roughly all sources can be well fitted if a small fraction of the steady-state electron energy is ejected into the nonthermal electrons. The size of the radio emission region of our model is around several thousands of gravitational radii, which is also roughly consistent with recent high-resolution VLBI observations for some nearby LLAGNs.

  9. Electron cloud observations at the ISIS Proton Synchrotron

    CERN Document Server

    Pertica, A.

    2013-04-22

    The build up of electron clouds inside a particle accelerator vacuum chamber can produce strong transverse and longitudinal beam instabilities which in turn can lead to high levels of beam loss often requiring the accelerator to be run below its design specification. To study the behaviour of electron clouds at the ISIS Proton Synchrotron, a Micro-Channel Plate (MCP) based electron cloud detector has been developed. The detector is based on the Retarding Field Analyser (RFA) design and consists of a retarding grid, which allows energy analysis of the electron signal, and a MCP assembly placed in front of the collector plate. The MCP assembly provides a current gain over the range 300 to 25K, thereby increasing the signal to noise ratio and dynamic range of the measurements. This paper presents the first electron cloud observations at the ISIS Proton Synchrotron. These results are compared against signals from a beam position monitor and a fast beam loss monitor installed at the same location.

  10. Observation of Electron Bernstein Wave Heating in the RFP

    Science.gov (United States)

    Seltzman, Andrew; Anderson, Jay; Goetz, John; Forest, Cary

    2017-10-01

    The first observation of RF heating in a reversed field pinch (RFP) using the electron Bernstein wave (EBW) has been demonstrated on MST. Efficient mode conversion of an outboard-launched X mode wave at 5.5 GHz leads to Doppler-shifted resonant absorption (ωrf = nωce-k||v||) for a broad range (n =1-7) of harmonics. The dynamics of EBW-heated electrons are measured using a spatial distribution of solid targets with diametrically opposed x-ray detectors. EBW heating produces a clear supra-thermal electron tail in MST. Radial deposition of the EBW is controlled with |B|and is measured using the HXR flux emitted from an insertable probe. In the thick-shelled MST RFP, the radial accessibility of EBW is limited to r/a >0.8 ( 10cm) by magnetic field error induced by the porthole necessary for the antenna. Experimental measurements show EBW propagation inward through a stochastic magnetic field. EBW-heated test electrons are used as a direct probe of edge (r/a >0.9) radial transport, showing a modest transition from `standard' to reduced-tearing RFP operation. Electron loss is too fast for collisional effects and implies a large non-collisional radial diffusivity. EBW heating has been demonstrated in reduced magnetic stochasticity plasmas with β = 15-20%. Work supported by USDOE.

  11. Current status of plasma emission electronics: II. Hardware

    Science.gov (United States)

    Bugaev, A. S.; Vizir, A. V.; Gushenets, V. I.; Nikolaev, A. G.; Oks, E. M.; Yushkov, G. Yu.; Burachevsky, Yu. A.; Burdovitsin, V. A.; Osipov, I. V.; Rempe, N. G.

    2003-04-01

    This paper is devoted to the engineering embodiment of the modern methods for producing charged ion and electron beams by extracting them from the plasma of a discharge. Electron beams use to execute electron-beam welding, annealing, and surface heating of materials and to realize plasmochemical reactions stimulated by fast electrons. Ion beams allow realization of technologies of ion implantation or ion-assisted deposition of coatings thereby opening new prospects for the creation of compounds and alloys by the method that makes it possible to obtain desired parameters and functional properties of the surface. A detailed description is given to the performance and design of devices producing beams of this type: the ion and electron sources being developed at the laboratory of plasma sources of the Institute of High-Current Electronics of the Russian Academy of Sciences and the laboratory of plasma electronics of Tomsk State University of Control Systems and Radioelectronics.

  12. Secondary electron emission characteristics of untreated and ion-textured titanium

    Science.gov (United States)

    Curren, Arthur N.; Jensen, Kenneth A.; Blackford, Gary A.

    1989-01-01

    Experimentally determined values of true secondary electron emission and relative values of reflected primary electron yield are presented for untreated (simply machined) and ion-textured, high-purity titanium over ranges of primary electron beam energies and beam impingement angles. The purpose of the investigation was to explore the feasibility of using titanium as electrode material in the multistage depressed collectors (MDC's) used in microwave amplifier traveling wave tubes (TWT's) for space communications and aircraft applications. Because of its relatively low density and thermal expansion characteristics and relatively high strength, thermal emissivity, and melting temperature, titanium presents itself as a possible candidate for the MDC electrode application. A detailed description of the method of ion texturing the titanium is included. Although the ion-treated surface considered in this study is not presented as being optimum from the standpoint of secondary electron emission suppression, it nevertheless serves to demonstrate that the surface can be modified by this procedure to significantly reduce these emission characteristics relative to those of the untreated surface. Further studies can reasonably be expected to produce surfaces with even lower secondary emission characteristics. The titanium surface were tested at primary electron beam energies of 200 to 2000 eV and at direct (0 deg) to near-grazing (85 deg) beam impingement angles. True secondary electron emission and relative reflected primary electron yield characteristics of the surfaces were compared with each other and with textured titanium surface exhibited secondary electron emission characteristics sharply lower than those exhibited by untreated titanium or copper. Clearly, then, in consideration of the secondary electron emission suppression of ion-textured titanium along with its other favorable physical properties, it must be included as a potential candidate for use as MDC electrode

  13. Methane emissions from Alaska in 2012 from CARVE airborne observations.

    Science.gov (United States)

    Chang, Rachel Y-W; Miller, Charles E; Dinardo, Steven J; Karion, Anna; Sweeney, Colm; Daube, Bruce C; Henderson, John M; Mountain, Marikate E; Eluszkiewicz, Janusz; Miller, John B; Bruhwiler, Lori M P; Wofsy, Steven C

    2014-11-25

    We determined methane (CH4) emissions from Alaska using airborne measurements from the Carbon Arctic Reservoirs Vulnerability Experiment (CARVE). Atmospheric sampling was conducted between May and September 2012 and analyzed using a customized version of the polar weather research and forecast model linked to a Lagrangian particle dispersion model (stochastic time-inverted Lagrangian transport model). We estimated growing season CH4 fluxes of 8 ± 2 mg CH4⋅m(-2)⋅d(-1) averaged over all of Alaska, corresponding to fluxes from wetlands of 56(-13)(+22) mg CH4⋅m(-2)⋅d(-1) if we assumed that wetlands are the only source from the land surface (all uncertainties are 95% confidence intervals from a bootstrapping analysis). Fluxes roughly doubled from May to July, then decreased gradually in August and September. Integrated emissions totaled 2.1 ± 0.5 Tg CH4 for Alaska from May to September 2012, close to the average (2.3; a range of 0.7 to 6 Tg CH4) predicted by various land surface models and inversion analyses for the growing season. Methane emissions from boreal Alaska were larger than from the North Slope; the monthly regional flux estimates showed no evidence of enhanced emissions during early spring or late fall, although these bursts may be more localized in time and space than can be detected by our analysis. These results provide an important baseline to which future studies can be compared.

  14. X-ray emission from relativistically moving electron density cusps

    Energy Technology Data Exchange (ETDEWEB)

    Kando, M.; Pirozhkov, A. S.; Nakamura, T.; Hayashi, Y.; Kotaki, H.; Kawase, K.; Esirkepov, T. Zh.; Fukuda, Y.; Kiriyama, H.; Okada, H.; Daito, I.; Kameshima, T.; Mori, M.; Koga, J. K.; Daido, H.; Faenov, A. Ya.; Pikuz, T.; Ma, J.; Chen, L.-M.; Ragozin, E. N. [Japan Atomic Energy Agency (Japan); Osaka University (Japan); Joint Institute for High Temperature of the Russian Academy of Science, Moscow (Russian Federation); Institute of Physics, Chinese Academy of Sciences, Beijing (China); P. N. Lebedev Physical Institute of the Russian Academy of Sciences, Leninsky prospekt 53, 119991 Moscow (Russian Federation); Japan Atomic Energy Agency and Graduate School for the Creation of New Photonics Industries (Japan); Ludwig-Maximilians-University (Germany); and others

    2012-07-11

    We report on novel methods to generate ultra-short, coherent, X-rays using a laserplasma interaction. Nonlinear interaction of intense laser pulses with plasma creates stable, specific structures such as electron cusps. For example, wake waves excited in an underdense plasma by an intense, short-pulse laser become dense and propagate along with the laser pulse. This is called a relativistic flying mirror. The flying mirror can reflect a counter-propagating laser pulse and directly convert it into high-frequency radiation, with a frequency multiplication factor of {approx} 4{gamma}{sup 2} and pulse shortening with the same factor. After the proof-of-principle experiments, we observed that the photon number generated in the flying mirror is close to the theoretical estimate. We present the details of the experiment in which a 9 TW laser pulse focused into a He gas jet generated the Flying Mirror, which partly reflected a 1 TW pulse, giving up to {approx} 10{sup 10} photons, 60 nJ (1.4 Multiplication-Sign 10{sup 12} photons/sr) in the XUV spectral region (12.8-22 nm).

  15. Secondary Electron Emission Materials for Transmission Dynodes in Novel Photomultipliers: A Review

    Directory of Open Access Journals (Sweden)

    Shu Xia Tao

    2016-12-01

    Full Text Available Secondary electron emission materials are reviewed with the aim of providing guidelines for the future development of novel transmission dynodes. Materials with reflection secondary electron yield higher than three and transmission secondary electron yield higher than one are tabulated for easy reference. Generations of transmission dynodes are listed in the order of the invention time with a special focus on the most recent atomic-layer-deposition synthesized transmission dynodes. Based on the knowledge gained from the survey of secondary election emission materials with high secondary electron yield, an outlook of possible improvements upon the state-of-the-art transmission dynodes is provided.

  16. NOx emission trends over Chinese cities estimated from OMI observations during 2005 to 2015

    Science.gov (United States)

    Liu, Fei; Beirle, Steffen; Zhang, Qiang; van der A, Ronald J.; Zheng, Bo; Tong, Dan; He, Kebin

    2017-08-01

    Satellite nitrogen dioxide (NO2) observations have been widely used to evaluate emission changes. To determine trends in nitrogen oxides (NOx) emission over China, we used a method independent of chemical transport models to quantify the NOx emissions from 48 cities and seven power plants over China, on the basis of Ozone Monitoring Instrument (OMI) NO2 observations from 2005 to 2015. We found that NOx emissions over 48 Chinese cities increased by 52 % from 2005 to 2011 and decreased by 21 % from 2011 to 2015. The decrease since 2011 could be mainly attributed to emission control measures in power sector; while cities with different dominant emission sources (i.e., power, industrial, and transportation sectors) showed variable emission decline timelines that corresponded to the schedules for emission control in different sectors. The time series of the derived NOx emissions was consistent with the bottom-up emission inventories for all power plants (r = 0. 8 on average), but not for some cities (r = 0. 4 on average). The lack of consistency observed for cities was most probably due to the high uncertainty of bottom-up urban emissions used in this study, which were derived from downscaling the regional-based emission data to city level by using spatial distribution proxies.

  17. NOx emission trends over Chinese cities estimated from OMI observations during 2005 to 2015

    Directory of Open Access Journals (Sweden)

    F. Liu

    2017-08-01

    Full Text Available Satellite nitrogen dioxide (NO2 observations have been widely used to evaluate emission changes. To determine trends in nitrogen oxides (NOx emission over China, we used a method independent of chemical transport models to quantify the NOx emissions from 48 cities and seven power plants over China, on the basis of Ozone Monitoring Instrument (OMI NO2 observations from 2005 to 2015. We found that NOx emissions over 48 Chinese cities increased by 52 % from 2005 to 2011 and decreased by 21 % from 2011 to 2015. The decrease since 2011 could be mainly attributed to emission control measures in power sector; while cities with different dominant emission sources (i.e., power, industrial, and transportation sectors showed variable emission decline timelines that corresponded to the schedules for emission control in different sectors. The time series of the derived NOx emissions was consistent with the bottom-up emission inventories for all power plants (r = 0. 8 on average, but not for some cities (r = 0. 4 on average. The lack of consistency observed for cities was most probably due to the high uncertainty of bottom-up urban emissions used in this study, which were derived from downscaling the regional-based emission data to city level by using spatial distribution proxies.

  18. Directed emission of CdSe nanoplatelets originating from strongly anisotropic 2D electronic structure

    Science.gov (United States)

    Scott, Riccardo; Heckmann, Jan; Prudnikau, Anatol V.; Antanovich, Artsiom; Mikhailov, Aleksandr; Owschimikow, Nina; Artemyev, Mikhail; Climente, Juan I.; Woggon, Ulrike; Grosse, Nicolai B.; Achtstein, Alexander W.

    2017-12-01

    Intrinsically directional light emitters are potentially important for applications in photonics including lasing and energy-efficient display technology. Here, we propose a new route to overcome intrinsic efficiency limitations in light-emitting devices by studying a CdSe nanoplatelets monolayer that exhibits strongly anisotropic, directed photoluminescence. Analysis of the two-dimensional k-space distribution reveals the underlying internal transition dipole distribution. The observed directed emission is related to the anisotropy of the electronic Bloch states governing the exciton transition dipole moment and forming a bright plane. The strongly directed emission perpendicular to the platelet is further enhanced by the optical local density of states and local fields. In contrast to the emission directionality, the off-resonant absorption into the energetically higher 2D-continuum of states is isotropic. These contrasting optical properties make the oriented CdSe nanoplatelets, or superstructures of parallel-oriented platelets, an interesting and potentially useful class of semiconductor-based emitters.

  19. Optical emission of graphene and electron-hole pair production induced by a strong terahertz field

    Science.gov (United States)

    Oladyshkin, I. V.; Bodrov, S. B.; Sergeev, Yu. A.; Korytin, A. I.; Tokman, M. D.; Stepanov, A. N.

    2017-10-01

    We report on experimental observation of optical emission of graphene induced by an intense terahertz (THz) pulse. P-doped chemical-vapor-deposition graphene with an initial Fermi energy of about 200 meV was used; optical photons were detected in the 2.0-3.5 eV range. Emission started when the THz field amplitude exceeded 100 kV/cm. For the THz fields from 200 to 300 kV/cm, the temperature of optical radiation was constant, while the number of emitted photons increased by several dozen times. This fact clearly indicates multiplication of electron-hole pairs induced by an external field and not electron heating. The experimental data are in good agreement with the theory of Landau-Zener interband transitions. It is shown theoretically that Landau-Zener transitions are possible even in the case of heavily doped graphene because the strong THz field removes quasiparticles from the region of interband transitions for several femtoseconds, which cancels the Pauli blocking effect.

  20. Statistical analysis of MMS observations of energetic electron escape observed at/beyond the dayside magnetopause

    Science.gov (United States)

    Cohen, Ian J.; Mauk, Barry H.; Anderson, Brian J.; Westlake, Joseph H.; Sibeck, David G.; Turner, Drew L.; Fennell, Joseph F.; Blake, J. Bern; Jaynes, Allison N.; Leonard, Trevor W.; Baker, Daniel N.; Spence, Harlan E.; Reeves, Geoff D.; Giles, Barbara J.; Strangeway, Robert J.; Torbert, Roy B.; Burch, James L.

    2017-09-01

    Observations from the Energetic Particle Detector (EPD) instrument suite aboard the Magnetospheric Multiscale (MMS) spacecraft show that energetic (greater than tens of keV) magnetospheric particle escape into the magnetosheath occurs commonly across the dayside. This includes the surprisingly frequent observation of magnetospheric electrons in the duskside magnetosheath, an unexpected result given assumptions regarding magnetic drift shadowing. The 238 events identified in the 40 keV electron energy channel during the first MMS dayside season that exhibit strongly anisotropic pitch angle distributions indicating monohemispheric field-aligned streaming away from the magnetopause. A review of the extremely rich literature of energetic electron observations beyond the magnetopause is provided to place these new observations into historical context. Despite the extensive history of such research, these new observations provide a more comprehensive data set that includes unprecedented magnetic local time (MLT) coverage of the dayside equatorial magnetopause/magnetosheath. These data clearly highlight the common escape of energetic electrons along magnetic field lines concluded to have been reconnected across the magnetopause. While these streaming escape events agree with prior studies which show strong correlation with geomagnetic activity (suggesting a magnetotail source) and occur most frequently during periods of southward IMF, the high number of duskside events is unexpected and previously unobserved. Although the lowest electron energy channel was the focus of this study, the events reported here exhibit pitch angle anisotropies indicative of streaming up to 200 keV, which could represent the magnetopause loss of >1 MeV electrons from the outer radiation belt.

  1. Experimental Development of Low-emittance Field-emission Electron Sources

    Energy Technology Data Exchange (ETDEWEB)

    Lueangaranwong, A. [Northern Illinois Univ., DeKalb, IL (United States). Northern Illinois Center for Accelerator & Detector Development; Buzzard, C. [Northern Illinois Univ., DeKalb, IL (United States); Divan, R. [Argonne National Lab. (ANL), Argonne, IL (United States). Center for Nanoscale Materials; Korampally, V. [Northern Illinois Univ., DeKalb, IL (United States); Piot, P. [Northern Illinois Univ., DeKalb, IL (United States). Northern Illinois Center for Accelerator & Detector Development; Fermi National Accelerator Lab. (FNAL), Batavia, IL (United States)

    2016-10-10

    Field emission electron sources are capable of extreme brightness when excited by static or time-dependent electro- magnetic fields. We are currently developing a cathode test stand operating in DC mode with possibility to trigger the emission using ultra-short (~ 100-fs) laser pulses. This contribution describes the status of an experiment to investigate field-emission using cathodes under development at NIU in collaboration with the Argonne’s Center for Nanoscale Materials.

  2. Electron emission from condensed phase material induced by fast protons†

    Science.gov (United States)

    Shinpaugh, J. L.; McLawhorn, R. A.; McLawhorn, S. L.; Carnes, K. D.; Dingfelder, M.; Travia, A.; Toburen, L. H.

    2011-01-01

    Monte Carlo track simulation has become an important tool in radiobiology. Monte Carlo transport codes commonly rely on elastic and inelastic electron scattering cross sections determined using theoretical methods supplemented with gas-phase data; experimental condensed phase data are often unavailable or infeasible. The largest uncertainties in the theoretical methods exist for low-energy electrons, which are important for simulating electron track ends. To test the reliability of these codes to deal with low-energy electron transport, yields of low-energy secondary electrons ejected from thin foils have been measured following passage of fast protons. Fast ions, where interaction cross sections are well known, provide the initial spectrum of low-energy electrons that subsequently undergo elastic and inelastic scattering in the material before exiting the foil surface and being detected. These data, measured as a function of the energy and angle of the emerging electrons, can provide tests of the physics of electron transport. Initial measurements from amorphous solid water frozen to a copper substrate indicated substantial disagreement with MC simulation, although questions remained because of target charging. More recent studies, using different freezing techniques, do not exhibit charging, but confirm the disagreement seen earlier between theory and experiment. One now has additional data on the absolute differential electron yields from copper, aluminum and gold, as well as for thin films of frozen hydrocarbons. Representative data are presented. PMID:21183539

  3. Modeling of the electron distribution based on bremsstrahlung emission during lower hybrid current drive on PLT

    Energy Technology Data Exchange (ETDEWEB)

    Stevens, J.E.; von Goeler, S.; Bernabei, S.; Bitter, M.; Chu, T.K.; Efthimion, P.; Fisch, N.; Hooke, W.; Hosea, J.; Jobes, F.

    1985-03-01

    Lower hybrid current drive requires the generation of a high energy electron tail anisotropic in velocity. Measurements of bremsstrahlung emission produced by this tail are compared with the calculated emission from reasonable model distributions. The physical basis and the sensitivity of this modeling process are described and the plasma properties of current driven discharges which can be derived from the model are discussed.

  4. Channeling, Volume Reection and Gamma Emission Using 14GeV Electrons in Bent Silicon Crystals

    Energy Technology Data Exchange (ETDEWEB)

    Benson, Brandon [SLAC National Accelerator Lab., Menlo Park, CA (United States)

    2015-08-14

    High energy electrons can be deflected with very tight bending radius using a bent silicon crystal. This produces gamma radiation. As these crystals can be thin, a series of bent silicon crystals with alternating direction has the potential to produce coherent gamma radiation with reasonable energy of the driving electron beam. Such an electron crystal undulator offers the prospect for higher energy radiation at lower cost than current methods. Permanent magnetic undulators like LCLS at SLAC National Accelerator Laboratory are expensive and very large (about 100 m in case of the LCLS undulator). Silicon crystals are inexpensive and compact when compared to the large magnetic undulators. Additionally, such a high energy coherent light source could be used for probing through materials currently impenetrable by x-rays. In this work we present the experimental data and analysis of experiment T523 conducted at SLAC National Accelerator Laboratory. We collected the spectrum of gamma ray emission from 14 GeV electrons on a bent silicon crystal counting single photons. We also investigated the dynamics of electron motion in the crystal i.e. processes of channeling and volume reflection at 14 GeV, extending and building off previous work. Our single photon spectrum for the amorphous crystal orientation is consistent with bremsstrahlung radiation and the volume reflection crystal orientation shows a trend consistent with synchrotron radiation at a critical energy of 740 MeV. We observe that in these two cases the data are consistent, but we make no further claims because of statistical limitations. We also extended the known energy range of electron crystal dechanneling length and channeling efficiency to 14 GeV.

  5. A computationally assisted spectroscopic technique to measure secondary electron emission coefficients in radio frequency plasmas

    CERN Document Server

    Daksha, M; Schuengel, E; Korolov, I; Derzsi, A; Koepke, M; Donko, Z; Schulze, J

    2016-01-01

    A Computationally Assisted Spectroscopic Technique to measure secondary electron emission coefficients ($\\gamma$-CAST) in capacitively-coupled radio-frequency plasmas is proposed. This non-intrusive, sensitive diagnostic is based on a combination of Phase Resolved Optical Emission Spectroscopy and particle-based kinetic simulations. In such plasmas (under most conditions in electropositive gases) the spatio-temporally resolved electron-impact excitation/ionization rate features two distinct maxima adjacent to each electrode at different times within each RF period. While one maximum is the consequence of the energy gain of electrons due to sheath expansion, the second maximum is produced by secondary electrons accelerated towards the plasma bulk by the sheath electric field at the time of maximum voltage drop across the adjacent sheath. Due to these different excitation/ionization mechanisms, the ratio of the intensities of these maxima is very sensitive to the secondary electron emission coefficient $\\gamma$...

  6. Electron Emission from Amorphous Solid Water Induced by Passage of Energetic Protons and Fluorine Ions

    Science.gov (United States)

    Toburen, L. H.; McLawhorn, S. L.; McLawhorn, R. A.; Carnes, K. D.; Dingfelder, M.; Shinpaugh, J. L.

    2013-01-01

    Absolute doubly differential electron emission yields were measured from thin films of amorphous solid water (ASW) after the transmission of 6 MeV protons and 19 MeV (1 MeV/nucleon) fluorine ions. The ASW films were frozen on thin (1-μm) copper foils cooled to approximately 50 K. Electrons emitted from the films were detected as a function of angle in both the forward and backward direction and as a function of the film thickness. Electron energies were determined by measuring the ejected electron time of flight, a technique that optimizes the accuracy of measuring low-energy electron yields, where the effects of molecular environment on electron transport are expected to be most evident. Relative electron emission yields were normalized to an absolute scale by comparison of the integrated total yields for proton-induced electron emission from the copper substrate to values published previously. The absolute doubly differential yields from ASW are presented along with integrated values, providing single differential and total electron emission yields. These data may provide benchmark tests of Monte Carlo track structure codes commonly used for assessing the effects of radiation quality on biological effectiveness. PMID:20681805

  7. Research of the Electron Cyclotron Emission with Vortex Property excited by high power high frequency Gyrotron

    Science.gov (United States)

    Goto, Yuki; Kubo, Shin; Tsujimura, Tohru; Takubo, Hidenori

    2017-10-01

    Recently, it has been shown that the radiation from a single electron in cyclotron motion has vortex property. Although the cyclotron emission exists universally in nature, the vortex property has not been featured because this property is normally cancelled out due to the randomness in gyro-phase of electrons and the development of detection of the vortex property has not been well motivated. In this research, we are developing a method to generate the vortex radiation from electrons in cyclotron motion with controlled gyro-phase. Electron that rotates around the uniform static magnetic field is accelerated by right-hand circular polarized (RHCP) radiation resonantly when the cyclotron frequency coincides with the applied RHCP radiation frequency. A large number of electrons can be coherently accelerated in gyro-phase by a RHCP high power radiation so that these electrons can radiate coherent emission with vortex feature. We will show that vortex radiation created by purely rotating electrons for the first time.

  8. Kinetic Theory and Fast Wind Observations of the Electron Strahl

    Science.gov (United States)

    Horaites, Konstantinos; Boldyrev, Stanislav; Wilson, Lynn B., III; Viñas, Adolfo F.; Merka, Jan

    2018-02-01

    We develop a model for the strahl population in the solar wind - a narrow, low-density and high-energy electron beam centred on the magnetic field direction. Our model is based on the solution of the electron drift-kinetic equation at heliospheric distances where the plasma density, temperature and the magnetic field strength decline as power laws of the distance along a magnetic flux tube. Our solution for the strahl depends on a number of parameters that, in the absence of the analytic solution for the full electron velocity distribution function (eVDF), cannot be derived from the theory. We however demonstrate that these parameters can be efficiently found from matching our solution with observations of the eVDF made by the Wind satellite's SWE strahl detector. The model is successful at predicting the angular width (FWHM) of the strahl for the Wind data at 1 au, in particular by predicting how this width scales with particle energy and background density. We find that the strahl distribution is largely determined by the local temperature Knudsen number γ ∼ |T dT/dx|/n, which parametrizes solar wind collisionality. We compute averaged strahl distributions for typical Knudsen numbers observed in the solar wind, and fit our model to these data. The model can be matched quite closely to the eVDFs at 1 au; however, it then overestimates the strahl amplitude at larger heliocentric distances. This indicates that our model may be improved through the inclusion of additional physics, possibly through the introduction of 'anomalous diffusion' of the strahl electrons.

  9. Observational and theoretical study of the point sources of very high energy gamma-ray emission

    Science.gov (United States)

    Babyk, Iurii

    2017-04-01

    The study of the sky using the most energetic photons plays a crucial role in detecting and exploring high-energy phenomena in the Universe. Observations conducted over recent years with new ground-based and space-borne gamma-ray instruments reveal that the universe is full of extreme accelerators, i.e., objects with surprisingly high efficiency for acceleration of electrons. In particular such an efficient acceleration is observed in gamma-ray-loud binary (GRLB) systems. GRLBs are a newly identified class of X-ray binaries in which interaction of an outflow from the compact object with the wind and radiation emitted by a companion star leads to the production of very-high-energy gamma-ray emission. Only five such systems have been firmly detected as persistent or regularly variable TeV gamma-ray emitters. All GRLBs detected in the TeV energy range contain a hot, young star and exhibit variable or periodic emission at multiple wavelengths across the electromagnetic spectrum. Details of the physical mechanism of the high-energy activity of GRLBs are not clear yet. Broad multi-wavelength observations are crucial to reveal the characteristic energies of the relativistic wind and better understanding of the nature of these sources. It looks quite possible that all these systems can be understood within the "hidden pulsar" model, and the observed differences are due to the different sizes of the system. In my work, I concentrate on the X-ray and gamma-ray emission observed from gamma-ray binaries PSR B1259-63 and LS I +61 303 with Suzaku, XMM-Newton, Swift, Chandra and Fermi observatories. In PSR B1259-63, the compact source is a young 48 ms radio pulsar orbiting Be-type star with period of 3.4 years. During my studies, I have been intensively involved in the analysis of the results of two multi-wavelength campaigns organized in 2010 and 2014 during the periastron passages in this system. These observations reveal complex spectral variability of the source as it passes

  10. Gas Desorption and Electron Emission from 1 MeV Potassium Iion Bombardment of Stainless Steel

    Energy Technology Data Exchange (ETDEWEB)

    Molvik, A; Covo, M K; Bieniosek, F; Prost, L; Seidl, P; Baca, D; Coorey, A; Sakumi, A

    2004-03-25

    Gas desorption and electron emission coefficients were measured for 1 MeV potassium ions incident on stainless steel at grazing angles (between 80 and 88 degrees from normal incidence) using a new gas-electron source diagnostic (GESD). Issues addressed in design and commissioning of the GESD include effects from backscattering of ions at the surface, space-charge limited emission current, and reproducibility of desorption measurements. We find that electron emission coefficients {gamma}{sub e} scale as 1/cos({theta}) up to angles of 86 degrees, where {gamma}{sub e} = 90. Nearer grazing incidence, {gamma}{sub e} is reduced below the 1/cos({theta}) scaling by nuclear scattering of ions through large angles, reaching {gamma}{sub e} = 135 at 88 degrees. Electrons were emitted with a measured temperature of {approx}30 eV. Gas desorption coefficients {gamma}{sub 0} were much larger, of order {gamma}{sub 0} = 10{sub 4}. They also varied with angle, but much more slowly than 1/cos({theta}). From this we conclude that the desorption was not entirely from adsorbed layers of gas on the surface. Two mitigation techniques were investigated: rough surfaces reduced electron emission by a factor of ten and gas desorption by a factor of two; a mild bake to {approx}220 degrees had no effect on electron emission, but decreased gas desorption by 15% near grazing incidence. We propose that gas desorption is due to electronic sputtering.

  11. Monte Carlo simulation of heavy ion induced kinetic electron emission from an Al surface

    CERN Document Server

    Ohya, K

    2002-01-01

    A Monte Carlo simulation is performed in order to study heavy ion induced kinetic electron emission from an Al surface. In the simulation, excitation of conduction band electrons by the projectile ion and recoiling target atoms is treated on the basis of the partial wave expansion method, and the cascade multiplication process of the excited electrons is simulated as well as collision cascade of the recoiling target atoms. Experimental electron yields near conventional threshold energies of heavy ions are simulated by an assumption of a lowering in the apparent surface barrier for the electrons. The present calculation derives components for electron excitations by the projectile ion, the recoiling target atoms and the electron cascades, from the calculated total electron yield. The component from the recoiling target atoms increases with increasing projectile mass, whereas the component from the electron cascade decreases. Although the components from the projectile ion and the electron cascade increase with...

  12. Factors affecting the performance of detectors that use secondary electron emission from a thin foil to determine ion impact position

    CERN Document Server

    Shapira, D; Hulett, L D; Ciao, Z

    2000-01-01

    The factors affecting the performance of a Position-Sensitive Timing Detector (PSTD), based on the detection of secondary electrons ejected from a thin foil by the passing ion, were investigated. Different contributions to the observed (generally poor) position resolution were investigated. The effects of multiple scattering in the foil were determined first. We then measured the contribution of the position-sensitive detector and signal-handling electronics. Finally, the effect of electron transport, from the point of emission at the foil surface to the micro-channel plate detector (MCP) surface, was measured and evaluated. Our measurements, as well as a simulation of the electron transport, lead us to conclude that for detectors with foil-to-MCP distance >=5 cm, electron transport limits the devices currently in use to resolution worse than 2 mm (FWHM).

  13. XMM Observations of X-Ray Emission from Supernovae

    Science.gov (United States)

    Immler, Stefan; Lewin, Walter

    2003-01-01

    Of the six proposed targets, only one observation was performed. The observation resulted in a 28ks observation of SN 1998S. At the time of writing the proposal, our target list only contained previously unknown X-ray supernovae. Between submission of the proposal and the actual observation, a Chandra DDT observation resulted in the detection of SN 1998S. Since SN 1998S was observed with Chandra five times before the XMM-Newton observation was made, the data did not yield enough new information to warrant a separate SN 1998S publication. The key science results of that observation were presented in a review article (by Immler and Lewin); the results were also presented at two conferences.

  14. Analysis of auroral infrared emissions observed during the ELIAS experiment

    Directory of Open Access Journals (Sweden)

    G. E. Caledonia

    Full Text Available The ELIAS (Earth Limb Infrared Atmospheric Structure experiment was flown from the Poker Flat Research Range, Alaska in 1983 and successfully monitored visible and infrared emissions from an IBC III+ aurora. Measurements were performed in both staring and scanning modes over several hundred seconds. The data for short- and mid-wave infrared regions have been analyzed in terms of auroral excitation of the NO and NO+ vibrational bands. Auroral excitation efficiencies and kinetic implications are presented.

  15. Aberration corrected 1.2-MV cold field-emission transmission electron microscope with a sub-50-pm resolution

    Energy Technology Data Exchange (ETDEWEB)

    Akashi, Tetsuya; Takahashi, Yoshio; Tanigaki, Toshiaki, E-mail: toshiaki.tanigaki.mv@hitachi.com; Shimakura, Tomokazu; Kawasaki, Takeshi; Furutsu, Tadao; Shinada, Hiroyuki; Osakabe, Nobuyuki [Central Research Laboratory, Hitachi, Ltd., Hatoyama 350-0395 (Japan); Müller, Heiko; Haider, Maximilian [Corrected Electron Optical Systems GmbH, Englerstr. 28, D-69126 Heidelberg (Germany); Tonomura, Akira [Central Research Laboratory, Hitachi, Ltd., Hatoyama 350-0395 (Japan); RIKEN Center for Emergent Matter Science (CEMS), Wako 351-0198 (Japan)

    2015-02-16

    Atomic-resolution electromagnetic field observation is critical to the development of advanced materials and to the unveiling of their fundamental physics. For this purpose, a spherical-aberration corrected 1.2-MV cold field-emission transmission electron microscope has been developed. The microscope has the following superior properties: stabilized accelerating voltage, minimized electrical and mechanical fluctuation, and coherent electron emission. These properties have enabled to obtain 43-pm information transfer. On the bases of these performances, a 43-pm resolution has been obtained by correcting lens aberrations up to the third order. Observations of GaN [411] thin crystal showed a projected atomic locations with a separation of 44 pm.

  16. Low latitude electron temperature observed by the CHAMP satellite

    DEFF Research Database (Denmark)

    Stolle, Claudia; Truhlik, V.; Richards, P.

    2012-01-01

    In recent years a growing number of satellite measurements in the ionosphere and thermosphere provide long and continuous data records which enable the investigation of climatological trends and the quantification of regular variations or isolated events. The CHAMP mission provides a valuable base...... Te morning overshoot (MO). Both, data and model revealed an anti-correlation between the equatorial MO amplitude and solar EUV flux at these altitudes. The CHAMP observations also reveal a post sunset electron temperature anomaly in analogy to the equatorial ionisation anomaly at altitudes below 400...

  17. Study of photon emission by electron capture during solar nuclei acceleration. 3: Photon production evaluations

    Science.gov (United States)

    Perez-Peraza, J.; Alvarez, M.; Gallegos, A.

    1985-01-01

    Lower limits of photon fluxes were evaluated from electron capture during acceleration in solar flares, because the arbitrary q sub c asterisk assumed in this work evolves very slow with velocity, probably much more slowly than the physical actual situation: in fact, more emission is expected toward the IR region. Nevertheless the authors claim to show that the factibility of sounding acceleration processes, charge evolution processes and physical parameters of the source itself, by the observational analysis of this kind of emissions. For instance, it would be interesting to search observationally, for the predicted flux and energy drift of F sub e ions interacting with the atomic 0 and F sub e of the source matter, or, even more feasible for the X-ray lines at 4.2 keV and 2.624 + 0.003 KeV from Fe and S ions in ionized Fe at T = 10 to the 7th power K respectively, the 418 + or - 2 eV and 20 + or - 4 eV lines of Fe and S in ionized Fe at 5 x 10 to the 6th power K, which are predicted from Fermi acceleration.

  18. Experimental observation of acoustic emissions generated by a pulsed proton beam from a hospital-based clinical cyclotron.

    Science.gov (United States)

    Jones, Kevin C; Vander Stappen, François; Bawiec, Christopher R; Janssens, Guillaume; Lewin, Peter A; Prieels, Damien; Solberg, Timothy D; Sehgal, Chandra M; Avery, Stephen

    2015-12-01

    To measure the acoustic signal generated by a pulsed proton spill from a hospital-based clinical cyclotron. An electronic function generator modulated the IBA C230 isochronous cyclotron to create a pulsed proton beam. The acoustic emissions generated by the proton beam were measured in water using a hydrophone. The acoustic measurements were repeated with increasing proton current and increasing distance between detector and beam. The cyclotron generated proton spills with rise times of 18 μs and a maximum measured instantaneous proton current of 790 nA. Acoustic emissions generated by the proton energy deposition were measured to be on the order of mPa. The origin of the acoustic wave was identified as the proton beam based on the correlation between acoustic emission arrival time and distance between the hydrophone and proton beam. The acoustic frequency spectrum peaked at 10 kHz, and the acoustic pressure amplitude increased monotonically with increasing proton current. The authors report the first observation of acoustic emissions generated by a proton beam from a hospital-based clinical cyclotron. When modulated by an electronic function generator, the cyclotron is capable of creating proton spills with fast rise times (18 μs) and high instantaneous currents (790 nA). Measurements of the proton-generated acoustic emissions in a clinical setting may provide a method for in vivo proton range verification and patient monitoring.

  19. Multi-field electron emission pattern of 2D emitter: Illustrated with graphene

    Science.gov (United States)

    Luo, Ma; Li, Zhibing

    2016-11-01

    The mechanism of laser-assisted multi-field electron emission of two-dimensional emitters is investigated theoretically. The process is basically a cold field electron emission but having more controllable components: a uniform electric field controls the emission potential barrier, a magnetic field controls the quantum states of the emitter, while an optical field controls electron populations of specified quantum states. It provides a highly orientational vacuum electron line source whose divergence angle over the beam plane is inversely proportional to square root of the emitter height. Calculations are carried out for graphene with the armchair emission edge, as a concrete example. The rate equation incorporating the optical excitation, phonon scattering, and thermal relaxation is solved in the quasi-equilibrium approximation for electron population in the bands. The far-field emission patterns, that inherit the features of the Landau bands, are obtained. It is found that the optical field generates a characteristic structure at one wing of the emission pattern.

  20. Particulate metals and organic compounds from electronic and tobacco-containing cigarettes: comparison of emission rates and secondhand exposure.

    Science.gov (United States)

    Saffari, Arian; Daher, Nancy; Ruprecht, Ario; De Marco, Cinzia; Pozzi, Paolo; Boffi, Roberto; Hamad, Samera H; Shafer, Martin M; Schauer, James J; Westerdahl, Dane; Sioutas, Constantinos

    2014-01-01

    In recent years, electronic cigarettes have gained increasing popularity as alternatives to normal (tobacco-containing) cigarettes. In the present study, particles generated by e-cigarettes and normal cigarettes have been analyzed and the degree of exposure to different chemical agents and their emission rates were quantified. Despite the 10-fold decrease in the total exposure to particulate elements in e-cigarettes compared to normal cigarettes, specific metals (e.g. Ni and Ag) still displayed a higher emission rate from e-cigarettes. Further analysis indicated that the contribution of e-liquid to the emission of these metals is rather minimal, implying that they likely originate from other components of the e-cigarette device or other indoor sources. Organic species had lower emission rates during e-cigarette consumption compared to normal cigarettes. Of particular note was the non-detectable emission of polycyclic aromatic hydrocarbons (PAHs) from e-cigarettes, while substantial emission of these species was observed from normal cigarettes. Overall, with the exception of Ni, Zn, and Ag, the consumption of e-cigarettes resulted in a remarkable decrease in secondhand exposure to all metals and organic compounds. Implementing quality control protocols on the manufacture of e-cigarettes would further minimize the emission of metals from these devices and improve their safety and associated health effects.

  1. Application of electronic nose for industrial odors and gaseous emissions measurement and monitoring--An overview.

    Science.gov (United States)

    Deshmukh, Sharvari; Bandyopadhyay, Rajib; Bhattacharyya, Nabarun; Pandey, R A; Jana, Arun

    2015-11-01

    The present review evaluates the key modules of the electronic nose, a biomimetic system, with specific examples of applications to industrial emissions monitoring and measurement. Regulations concerning the odor control are becoming very strict, due to ever mounting environmental pollution and its subsequent consequences and it is advantageous to employ real time measurement system. In this perspective, systems like the electronic nose are an improved substitute for assessing the complex industrial emissions over other analytical techniques (odorant concentration measurement) and olfactometry (odor concentration measurement). Compared to tools like gas chromatography, electronic nose systems are easy to develop, are non-destructive and useful for both laboratory and on field purposes. Although there has been immense development of more sensitive and selective sensor arrays and advanced data mining techniques, there have been limited reports on the application of electronic nose for the measurement of industrial emissions. The current study sheds light on the practical applicability of electronic nose for the effective industrial odor and gaseous emissions measurement. The applications categorization is based on gaseous pollutants released from the industries. Calibration and calibration transfer methodologies have been discussed to enhance the applicability of electronic nose system. Further, industrial gas grab sampling technique is reviewed. Lastly, the electronic mucosa system, which has the ability to overcome the flaws of electronic nose system, has been examined. The review ends with the concluding remarks describing the pros and cons of artificial olfaction technique for the industrial applications. Copyright © 2015 Elsevier B.V. All rights reserved.

  2. Electrostatic Charging of Lunar Dust by UV Photoelectric Emissions and Solar Wind Electrons

    Science.gov (United States)

    Abbas, Mian M.; Tankosic, Dragana; Spann, James f.; LeClair, Andre C.; Dube, Michael J.

    2008-01-01

    The ubiquitous presence of dust in the lunar environment with its high adhesive characteristics has been recognized to be a major safety issue that must be addressed in view of its hazardous effects on robotic and human exploration of the Moon. The reported observations of a horizon glow and streamers at the lunar terminator during the Apollo missions are attributed to the sunlight scattered by the levitated lunar dust. The lunar surface and the dust grains are predominantly charged positively by the incident UV solar radiation on the dayside and negatively by the solar wind electrons on the night-side. The charged dust grains are levitated and transported over long distances by the established electric fields. A quantitative understanding of the lunar dust phenomena requires development of global dust distribution models, based on an accurate knowledge of lunar dust charging properties. Currently available data of lunar dust charging is based on bulk materials, although it is well recognized that measurements on individual dust grains are expected to be substantially different from the bulk measurements. In this paper we present laboratory measurements of charging properties of Apollo 11 & 17 dust grains by UV photoelectric emissions and by electron impact. These measurements indicate substantial differences of both qualitative and quantitative nature between dust charging properties of individual micron/submicron sized dust grains and of bulk materials. In addition, there are no viable theoretical models available as yet for calculation of dust charging properties of individual dust grains for both photoelectric emissions and electron impact. It is thus of paramount importance to conduct comprehensive measurements for charging properties of individual dust grains in order to develop realistic models of dust processes in the lunar atmosphere, and address the hazardous issues of dust on lunar robotic and human missions.

  3. Observation of Electron Neutrino Appearance in a Muon Neutrino Beam

    CERN Document Server

    Abe, K; Aihara, H; Akiri, T; Andreopoulos, C; Aoki, S; Ariga, A; Ariga, T; Assylbekov, S; Autiero, D; Barbi, M; Barker, G J; Barr, G; Bass, M; Batkiewicz, M; Bay, F; Bentham, S W; Berardi, V; Berger, B E; Berkman, S; Bertram, I; Bhadra, S; Blaszczyk, F d M; Blondel, A; Bojechko, C; Bordoni, S; Boyd, S B; Brailsford, D; Bravar, A; Bronner, C; Buchanan, N; Calland, R G; Rodríguez, J Caravaca; Cartwright, S L; Castillo, R; Catanesi, M G; Cervera, A; Cherdack, D; Christodoulou, G; Clifton, A; Coleman, J; Coleman, S J; Collazuol, G; Connolly, K; Cremonesi, L; Dabrowska, A; Danko, I; Das, R; Davis, S; de Perio, P; De Rosa, G; Dealtry, T; Dennis, S R; Densham, C; Di Lodovico, F; Di Luise, S; Drapier, O; Duboyski, T; Duffy, K; Dufour, F; Dumarchez, J; Dytman, S; Dziewiecki, M; Emery, S; Ereditato, A; Escudero, L; Finch, A J; Floetotto, L; Friend, M; Fujii, Y; Fukuda, Y; Furmanski, A P; Galymov, V; Gaudin, A; Giffin, S; Giganti, C; Gilje, K; Goeldi, D; Golan, T; Gomez-Cadenas, J J; Gonin, M; Grant, N; Gudin, D; Hadley, D R; Haesler, A; Haigh, M D; Hamilton, P; Hansen, D; Hara, T; Hartz, M; Hasegawa, T; Hastings, N C; Hayato, Y; Hearty, C; Helmer, R L; Hierholzer, M; Hignight, J; Hillairet, A; Himmel, A; Hiraki, T; Hirota, S; Holeczek, J; Horikawa, S; Huang, K; Ichikawa, A K; Ieki, K; Ieva, M; Ikeda, M; Imber, J; Insler, J; Irvine, T J; Ishida, T; Ishii, T; Ives, S J; Iyogi, K; Izmaylov, A; Jacob, A; Jamieson, B; Johnson, R A; Jo, J H; Jonsson, P; Jung, C K; Kaboth, A C; Kajita, T; Kakuno, H; Kameda, J; Kanazawa, Y; Karlen, D; Karpikov, I; Kearns, E; Khabibullin, M; Khotjantsev, A; Kielczewska, D; Kikawa, T; Kilinski, A; Kim, J; Kisiel, J; Kitching, P; Kobayashi, T; Koch, L; Kolaceke, A; Konaka, A; Kormos, L L; Korzenev, A; Koseki, K; Koshio, Y; Kreslo, I; Kropp, W; Kubo, H; Kudenko, Y; Kumaratunga, S; Kurjata, R; Kutter, T; Lagoda, J; Laihem, K; Lamont, I; Laveder, M; Lawe, M; Lazos, M; Lee, K P; Licciardi, C; Lindner, T; Lister, C; Litchfield, R P; Longhin, A; Ludovici, L; Macaire, M; Magaletti, L; Mahn, K; Malek, M; Manly, S; Marino, A D; Marteau, J; Martin, J F; Maruyama, T; Marzec, J; Mathie, E L; Matveev, V; Mavrokoridis, K; Mazzucato, E; McCarthy, M; McCauley, N; McFarland, K S; McGrew, C; Metelko, C; Mijakowski, P; Miller, C A; Minamino, A; Mineev, O; Mine, S; Missert, A; Miura, M; Monfregola, L; Moriyama, S; Mueller, Th A; Murakami, A; Murdoch, M; Murphy, S; Myslik, J; Nagasaki, T; Nakadaira, T; Nakahata, M; Nakai, T; Nakamura, K; Nakayama, S; Nakaya, T; Nakayoshi, K; Naples, D; Nielsen, C; Nirkko, M; Nishikawa, K; Nishimura, Y; O'Keeffe, H M; Ohta, R; Okumura, K; Okusawa, T; Oryszczak, W; Oser, S M; Owen, R A; Oyama, Y; Palladino, V; Paolone, V; Payne, D; Pearce, G F; Perevozchikov, O; Perkin, J D; Petrov, Y; Pickard, L J; Guerra, E S Pinzon; Pistillo, C; Plonski, P; Poplawska, E; Popov, B; Posiadala, M; Poutissou, J -M; Poutissou, R; Przewlocki, P; Quilain, B; Radicioni, E; Ratoff, P N; Ravonel, M; Rayner, M A M; Redij, A; Reeves, M; Reinherz-Aronis, E; Retiere, F; Robert, A; Rodrigues, P A; Rondio, E; Roth, S; Rubbia, A; Ruterbories, D; Sacco, R; Sakashita, K; Sánchez, F; Sato, F; Scantamburlo, E; Scholberg, K; Schwehr, J; Scott, M; Seiya, Y; Sekiguchi, T; Sekiya, H; Sgalaberna, D; Shiozawa, M; Short, S; Shustrov, Y; Sinclair, P; Smith, B; Smith, R J; Smy, M; Sobczyk, J T; Sobel, H; Sorel, M; Southwell, L; Stamoulis, P; Steinmann, J; Still, B; Suda, Y; Suzuki, A; Suzuki, K; Suzuki, S Y; Suzuki, Y; Szeglowski, T; Tacik, R; Tada, M; Takahashi, S; Takeda, A; Takeuchi, Y; Tanaka, H K; Tanaka, H A; Tanaka, M M; Terhorst, D; Terri, R; Thompson, L F; Thorley, A; Tobayama, S; Toki, W; Tomura, T; Totsuka, Y; Touramanis, C; Tsukamoto, T; Tzanov, M; Uchida, Y; Ueno, K; Vacheret, A; Vagins, M; Vasseur, G; Wachala, T; Waldron, A V; Walter, C W; Wark, D; Wascko, M O; Weber, A; Wendell, R; Wilkes, R J; Wilking, M J; Wilkinson, C; Williamson, Z; Wilson, J R; Wilson, R J; Wongjirad, T; Yamada, Y; Yamamoto, K; Yanagisawa, C; Yen, S; Yershov, N; Yokoyama, M; Yuan, T; Zalewska, A; Zalipska, J; Zambelli, L; Zaremba, K; Ziembicki, M; Zimmerman, E D; Zito, M; Żmuda, J

    2013-01-01

    The T2K experiment has observed electron neutrino appearance in a muon neutrino beam produced 295 km from the Super-Kamiokande detector with a peak energy of 0.6 GeV. A total of 28 electron neutrino events were detected with an energy distribution consistent with an appearance signal, corresponding to a significance of 7.3$\\sigma$ when compared to 4.92 $\\pm$ 0.55 expected background events. In the PMNS mixing model, the electron neutrino appearance signal depends on several parameters including three mixing angles $\\theta_{12}$, $\\theta_{23}$, $\\theta_{13}$, a mass difference $\\Delta m^2_{32}$ and a CP violating phase $\\delta_{\\mathrm{CP}}$. In this neutrino oscillation scenario, assuming $|\\Delta m^2_{32}| = 2.4 \\times 10^{-3}$ $\\rm eV^2$, $\\sin^2 \\theta_{23} = 0.5$, $\\delta_{\\mathrm{CP}}=0$, and $\\Delta m^2_{32} >0$ ($\\Delta m^2_{32} <0$), a best-fit value of $\\sin^2 2 \\theta_{13}$ = $0.140^{+0.038}_{-0.032}$ ($0.170^{+0.045}_{-0.037}$) is obtained.

  4. Observation of Electron Neutrino Appearance in a Muon Neutrino Beam

    Science.gov (United States)

    Abe, K.; Adam, J.; Aihara, H.; Akiri, T.; Andreopoulos, C.; Aoki, S.; Ariga, A.; Ariga, T.; Assylbekov, S.; Autiero, D.; Barbi, M.; Barker, G. J.; Barr, G.; Bass, M.; Batkiewicz, M.; Bay, F.; Bentham, S. W.; Berardi, V.; Berger, B. E.; Berkman, S.; Bertram, I.; Bhadra, S.; Blaszczyk, F. d. M.; Blondel, A.; Bojechko, C.; Bordoni, S.; Boyd, S. B.; Brailsford, D.; Bravar, A.; Bronner, C.; Buchanan, N.; Calland, R. G.; Caravaca Rodríguez, J.; Cartwright, S. L.; Castillo, R.; Catanesi, M. G.; Cervera, A.; Cherdack, D.; Christodoulou, G.; Clifton, A.; Coleman, J.; Coleman, S. J.; Collazuol, G.; Connolly, K.; Cremonesi, L.; Dabrowska, A.; Danko, I.; Das, R.; Davis, S.; de Perio, P.; De Rosa, G.; Dealtry, T.; Dennis, S. R.; Densham, C.; Di Lodovico, F.; Di Luise, S.; Drapier, O.; Duboyski, T.; Duffy, K.; Dufour, F.; Dumarchez, J.; Dytman, S.; Dziewiecki, M.; Emery, S.; Ereditato, A.; Escudero, L.; Finch, A. J.; Floetotto, L.; Friend, M.; Fujii, Y.; Fukuda, Y.; Furmanski, A. P.; Galymov, V.; Gaudin, A.; Giffin, S.; Giganti, C.; Gilje, K.; Goeldi, D.; Golan, T.; Gomez-Cadenas, J. J.; Gonin, M.; Grant, N.; Gudin, D.; Hadley, D. R.; Haesler, A.; Haigh, M. D.; Hamilton, P.; Hansen, D.; Hara, T.; Hartz, M.; Hasegawa, T.; Hastings, N. C.; Hayato, Y.; Hearty, C.; Helmer, R. L.; Hierholzer, M.; Hignight, J.; Hillairet, A.; Himmel, A.; Hiraki, T.; Hirota, S.; Holeczek, J.; Horikawa, S.; Huang, K.; Ichikawa, A. K.; Ieki, K.; Ieva, M.; Ikeda, M.; Imber, J.; Insler, J.; Irvine, T. J.; Ishida, T.; Ishii, T.; Ives, S. J.; Iyogi, K.; Izmaylov, A.; Jacob, A.; Jamieson, B.; Johnson, R. A.; Jo, J. H.; Jonsson, P.; Jung, C. K.; Kaboth, A. C.; Kajita, T.; Kakuno, H.; Kameda, J.; Kanazawa, Y.; Karlen, D.; Karpikov, I.; Kearns, E.; Khabibullin, M.; Khotjantsev, A.; Kielczewska, D.; Kikawa, T.; Kilinski, A.; Kim, J.; Kisiel, J.; Kitching, P.; Kobayashi, T.; Koch, L.; Kolaceke, A.; Konaka, A.; Kormos, L. L.; Korzenev, A.; Koseki, K.; Koshio, Y.; Kreslo, I.; Kropp, W.; Kubo, H.; Kudenko, Y.; Kumaratunga, S.; Kurjata, R.; Kutter, T.; Lagoda, J.; Laihem, K.; Lamont, I.; Laveder, M.; Lawe, M.; Lazos, M.; Lee, K. P.; Licciardi, C.; Lindner, T.; Lister, C.; Litchfield, R. P.; Longhin, A.; Ludovici, L.; Macaire, M.; Magaletti, L.; Mahn, K.; Malek, M.; Manly, S.; Marino, A. D.; Marteau, J.; Martin, J. F.; Maruyama, T.; Marzec, J.; Mathie, E. L.; Matveev, V.; Mavrokoridis, K.; Mazzucato, E.; McCarthy, M.; McCauley, N.; McFarland, K. S.; McGrew, C.; Metelko, C.; Mezzetto, M.; Mijakowski, P.; Miller, C. A.; Minamino, A.; Mineev, O.; Mine, S.; Missert, A.; Miura, M.; Monfregola, L.; Moriyama, S.; Mueller, Th. A.; Murakami, A.; Murdoch, M.; Murphy, S.; Myslik, J.; Nagasaki, T.; Nakadaira, T.; Nakahata, M.; Nakai, T.; Nakamura, K.; Nakayama, S.; Nakaya, T.; Nakayoshi, K.; Naples, D.; Nielsen, C.; Nirkko, M.; Nishikawa, K.; Nishimura, Y.; O'Keeffe, H. M.; Ohta, R.; Okumura, K.; Okusawa, T.; Oryszczak, W.; Oser, S. M.; Owen, R. A.; Oyama, Y.; Palladino, V.; Paolone, V.; Payne, D.; Pearce, G. F.; Perevozchikov, O.; Perkin, J. D.; Petrov, Y.; Pickard, L. J.; Pinzon Guerra, E. S.; Pistillo, C.; Plonski, P.; Poplawska, E.; Popov, B.; Posiadala, M.; Poutissou, J.-M.; Poutissou, R.; Przewlocki, P.; Quilain, B.; Radicioni, E.; Ratoff, P. N.; Ravonel, M.; Rayner, M. A. M.; Redij, A.; Reeves, M.; Reinherz-Aronis, E.; Retiere, F.; Robert, A.; Rodrigues, P. A.; Rojas, P.; Rondio, E.; Roth, S.; Rubbia, A.; Ruterbories, D.; Sacco, R.; Sakashita, K.; Sánchez, F.; Sato, F.; Scantamburlo, E.; Scholberg, K.; Schwehr, J.; Scott, M.; Seiya, Y.; Sekiguchi, T.; Sekiya, H.; Sgalaberna, D.; Shiozawa, M.; Short, S.; Shustrov, Y.; Sinclair, P.; Smith, B.; Smith, R. J.; Smy, M.; Sobczyk, J. T.; Sobel, H.; Sorel, M.; Southwell, L.; Stamoulis, P.; Steinmann, J.; Still, B.; Suda, Y.; Suzuki, A.; Suzuki, K.; Suzuki, S. Y.; Suzuki, Y.; Szeglowski, T.; Tacik, R.; Tada, M.; Takahashi, S.; Takeda, A.; Takeuchi, Y.; Tanaka, H. K.; Tanaka, H. A.; Tanaka, M. M.; Terhorst, D.; Terri, R.; Thompson, L. F.; Thorley, A.; Tobayama, S.; Toki, W.; Tomura, T.; Totsuka, Y.; Touramanis, C.; Tsukamoto, T.; Tzanov, M.; Uchida, Y.; Ueno, K.; Vacheret, A.; Vagins, M.; Vasseur, G.; Wachala, T.; Waldron, A. V.; Walter, C. W.; Wark, D.; Wascko, M. O.; Weber, A.; Wendell, R.; Wilkes, R. J.; Wilking, M. J.; Wilkinson, C.; Williamson, Z.; Wilson, J. R.; Wilson, R. J.; Wongjirad, T.; Yamada, Y.; Yamamoto, K.; Yanagisawa, C.; Yen, S.; Yershov, N.; Yokoyama, M.; Yuan, T.; Zalewska, A.; Zalipska, J.; Zambelli, L.; Zaremba, K.; Ziembicki, M.; Zimmerman, E. D.; Zito, M.; Żmuda, J.; T2K Collaboration

    2014-02-01

    The T2K experiment has observed electron neutrino appearance in a muon neutrino beam produced 295 km from the Super-Kamiokande detector with a peak energy of 0.6 GeV. A total of 28 electron neutrino events were detected with an energy distribution consistent with an appearance signal, corresponding to a significance of 7.3σ when compared to 4.92±0.55 expected background events. In the Pontecorvo-Maki-Nakagawa-Sakata mixing model, the electron neutrino appearance signal depends on several parameters including three mixing angles θ12, θ23, θ13, a mass difference Δm322 and a CP violating phase δCP. In this neutrino oscillation scenario, assuming |Δm322|=2.4×10-3 eV2, sin2θ23=0.5, and Δm322>0 (Δm322<0), a best-fit value of sin22θ13=0.140-0.032+0.038 (0.170-0.037+0.045) is obtained at δCP=0. When combining the result with the current best knowledge of oscillation parameters including the world average value of θ13 from reactor experiments, some values of δCP are disfavored at the 90% C.L.

  5. Electron Emission from Nano and MicroStructured Materials for Plasma Applications

    Science.gov (United States)

    Patino, Marlene; Raitses, Yevgeny; Wirz, Richard

    2016-09-01

    Secondary electron emission (SEE) from plasma-confining walls can lead to adverse effects (e.g. increased plasma heat flux to the wall) in plasma devices, including plasma processing, confinement fusion, and plasma thrusters. Reduction in SEE from engineered materials with nm to mm-sized structures (grooves, pores, fibers), has been previously observed for primary electrons incident normal to the material. Here we present SEE measurements from one such engineered material, carbon velvet with microfibers (5 μm diameter, 1-2 mm length), and from a plasma-structured material, tungsten fuzz with nm fibers (35-50 nm diameter, 100-200 nm length). Additionally, dependence of SEE on incident angle was explored for tungsten fuzz. Results for carbon velvet and tungsten fuzz at normal incidence show 75% and 50% decrease in total yield from smooth graphite and tungsten, respectively. More notable is the independence of SEE on the incident angle for tungsten fuzz, as opposed to inverse cosine dependence for smooth materials. Hence, the reduction in SEE from tungsten fuzz is more pronounced at grazing angles. This is important for plasma-facing materials where a retarding plasma sheath leads to increased likelihood of plasma electrons impacting at grazing angles. This work was supported by DOE contract DE-AC02-09CH11466; AFOSR grants FA9550-14-1-0053, FA9550-11-1-0282, AF9550-09-1-0695, and FA9550-14-10317; and DOE Office of Science Graduate Student Research Program.

  6. Microstructure-Sensitive Investigation of Fracture Using Acoustic Emission Coupled With Electron Microscopy

    Science.gov (United States)

    Wisner, Brian; Cabal, Mike; Vanniamparambiland, Prashanth A.; Leser, William; Hochhalter, Jacob; Kontsos, Antonios

    2015-01-01

    A novel technique using Scanning Electron Microscopy (SEM) in conjunction with Acoustic Emission (AE) monitoring is proposed to investigate microstructure-sensitive fatigue and fracture of metals. The coupling between quasi in situ microscopy with actual in situ nondestructive evaluation falls into the ICME framework and the idea of quantitative data-driven characterization of material behavior. To validate the use of AE monitoring inside the SEM chamber, Aluminum 2024-B sharp notch specimen were tested both inside and outside the microscope using a small scale mechanical testing device. Subsequently, the same type of specimen was tested inside the SEM chamber. Load data were correlated with both AE information and observations of microcracks around grain boundaries as well as secondary cracks, voids, and slip bands. The preliminary results are in excellent agreement with similar findings at the mesoscale. Extensions of the application of this novel technique are discussed.

  7. Nitrogen plasma formation through terahertz-induced ultrafast electron field emission

    DEFF Research Database (Denmark)

    Iwaszczuk, Krzysztof; Zalkovskij, Maksim; Strikwerda, Andrew

    2015-01-01

    . Terahertz (THz) radiation, commonly understood to be nonionizing due to its low photon energy, is here shown to produce electron field emission. We demonstrate that a carrier-envelope phase-stable single-cycle optical field at THz frequencies interacting with a metallic microantenna can generate...... and accelerate ultrashort and ultrabright electron bunches into free space, and we use these electrons to excite and ionize ambient nitrogen molecules near the antenna. The associated UV emission from the gas forms a novel THz wave detector, which, in contrast with conventional photon-counting or heat...

  8. Inversion of Ionospheric Electron Density from GPS Beacon Observations

    Institute of Scientific and Technical Information of China (English)

    Zou Yu-hua; Xu Ji-sheng

    2003-01-01

    This paper studies the mathematical foundation of time-dependent three-dimensional (3-D) computerized ionospheric tomography (CIT) for reconstructing ionospheric electron density, Ne, from ground-based GPS beacon observations. After simplifying the relation between Ne and time,the time-dependent 3-D inversion in consideration is reduced to a 3-D tomography with incomplete projections.To see clearly the effects of the incompleteness on the quality of reconstruction under 3-D condition, the formula of 3-D parallel-beam tomography is deduced theoretically. After establishing the mathematical foundation, simulations based on actual GPS ray paths with the help of the IRI-90 model are performed,and reasonable time-dependent 3-D distribution images of Neare obtained when taking proper layout of the network and allowing variable resolutions. The quality of the reconstruction is rather good when compared with the images from the IRI-90 model directly. Therefore, results in this paper demon-strate that imaging of the ionospheric electron density distri-bution from GPS beacon observations is reasonable in theory and feasible in practice.

  9. Inversion of Ionospheric Electron Density from GPS Beacon Observations

    Institute of Scientific and Technical Information of China (English)

    ZouYu-hua; XuJi-sheng

    2003-01-01

    This paper studies the mathematical foundation of time-dependent three-dimensional (3-D) computerized ionospheric tomography (CIT) for reconstructing ionospheric electron density, N~, from ground-based GPS beacon observations. After simplifying the relation between N. and time,the time-dependent 3-D inversion in consideration is reduced to a 3-D tomography with incomplete projections. To see clearly the effects of the incompleteness on the quality of reconstruction under 3-D condition, the formula of 3-D parallelbeam tomogtTaphy is deduced theoretically. After establishing the mathematical foundation, simulations based on actual GPS ray paths with the help of the IRI-90 model are performed,and reasonable time-dependent 3-D distribution images of Ne are obtained when taking proper layout of the network and allowing variable resolutions. The quality of the reconstruction is rather good when compared with the images from the IRI-90 model directly. Therefore, results in this paper demonstrate that imaging of the ionospheric electron density distribution from GPS beacon observations is reasonable in theor yand feasible in practice.

  10. Comparative Study on Electronic, Emission, Spontaneous Property of Porous Silicon in Different Solvents

    Directory of Open Access Journals (Sweden)

    M. Naziruddin Khan

    2014-01-01

    Full Text Available Luminescent porous silicon (Psi fabricated by simple chemical etching technique in different organic solvents was studied. By quantifying the silicon wafer piece, optical properties of the Psi in solutions were investigated. Observation shows that no photoluminescence light of Psi in all solvents is emitted. Morphology of Psi in different solvents indicates that the structure and distribution of Psi are differently observed. Particles are uniformly dispersive with the sizes around more or less 5–8 nm. The crystallographic plane and high crystalline nature of Psi is observed by selected area diffraction (SED and XRD. Electronic properties of Psi in solutions are influenced due to the variation of quantity of wafer and nature of solvent. Influence in band gaps of Psi calculated by Tauc’s method is obtained due to change of absorption edge of Psi in solvents. PL intensities are observed to be depending on quantity of silicon wafer, etched cross-section area on wafer surface. Effects on emission peaks and bands of Psi under temperature annealing are observed. The spontaneous signals of Psi measured under high power Pico second laser 355 nm source are significant, influenced by the nature of solvent, pumped energy, and quantity of Si wafer piece used in etching process.

  11. Identification of natural plasma emissions observed close to the plasmapause by the Cluster-Whisper relaxation sounder

    Directory of Open Access Journals (Sweden)

    P. Canu

    Full Text Available We use the data collected by the Whisper instrument onboard the Cluster spacecraft for a first test of its capabilities in the identification of the natural plasma waves observed in the Earth’s magnetosphere. The main signatures observed at the plasma frequency, upper hybrid frequency, and electron Bernstein modes were often difficult to be reliably recognized on previous missions. We use here the characteristic frequencies provided by the resonances triggered by the relaxation sounder of Whisper to identify with good confidence the various signatures detected in the complex wave spectra collected close to the plasmapause. Coupled with the good sensitivity, frequency and time resolution of Whisper, the resonances detected by the sounder allow one to precisely spot these natural emissions. This first analysis seems to confirm the interpretation of Geos observations: the natural emissions observed in Bernstein modes above the plasma frequency, now widely observed onboard Cluster, are not modeled by a single Maxwellian electrons distribution function. Therefore, multi-temperature electron distribution functions should be considered.

    Key words. Space plasma physics (active perturbation experiments; waves and instabilities; instrument and techniques

  12. First estimates of volume distribution of HF-pump enhanced emissions at 6300 and 5577 Å: a comparison between observations and theory

    Directory of Open Access Journals (Sweden)

    B. Gustavsson

    2008-12-01

    Full Text Available We present bi-static observations of radio-wave induced optical emissions at 6300 and 5577 Å from a night-time radio-induced optical emission ionospheric pumping experiment at the HIPAS (Fairbanks facility in Alaska. The optical observations were made at HIPAS and from HAARP located 285 km south-east. From these observations the altitude distribution of the emissions is estimated with tomography-like methods. These estimates are compared with theoretical models. Other diagnostics used to support the theoretical calculations include the new Poker Flat AMISR UHF radar near HIPAS. We find that the altitude distribution of the emissions agree with electron transport modeling with a source of accelerated electrons located 20 km below the upper-hybrid altitude.

  13. Secondary electron emission of tin and tin-lithium under low energy helium plasma exposure

    NARCIS (Netherlands)

    Kvon, V.; Oyarzabal, E.; Zoethout, E.; Martin-Rojo, A. B.; Morgan, T. W.; Tabares, F. L.

    2017-01-01

    Secondary electron emission (SEE) yields of tin (Sn) and tin-lithium (SnLi) eutectic (20 at.% Li) samples were measured in He-plasma at a mean incoming electron energy up to 120 eV. SnLi shows a maximum yield of about 1.45 at 110 eV electron energy while the yield of the Sn surface was measured to

  14. Double-beta decay with emission of single free electron

    Science.gov (United States)

    Babič, A.; Štefánik, D.; Krivoruchenko, M. I.; Šimkovic, F.

    2017-10-01

    We study a new mode of the neutrinoless and two-neutrino double-beta decays in which one of the electrons is emitted from the atom, while the other is directly produced in one of the available s1/2 or p1/2 subshells of the daughter ion. We calculate the phase-space factors, estimate the half-lives and derive the single-electron spectra for 0+ → 0+ ground-state nuclear transitions of the most relevant double-beta-decay isotopes: 48Ca, 76Ge, 82Se, 100Mo, 136Xe and 150Nd. The relativistic electron wave functions are evaluated at the nuclear radius by means of the multiconfiguration Dirac-Hartree-Fock package Grasp2K. We discuss the prospects for detecting these new modes in the tracking-and-calorimetry experiments NEMO-3 and SuperNEMO.

  15. Bounds on Majoron emission from muon to electron conversion experiments

    Science.gov (United States)

    Garcia I Tormo, Xavier; Bryman, Douglas; Czarnecki, Andrzej; Dowling, Matthew

    2011-12-01

    In models where lepton number is considered to be a spontaneously broken global symmetry a massless Goldstone boson, the Majoron (J), appears. We describe a procedure to explore the muon-electron-Majoron coupling using the results from μ-e conversion search experiments. To accomplish that, we determine how the energy spectrum of the muon decay into an electron and a Majoron is modified by binding effects in a muonic atom. We find that the future μ→e conversion experiments may be able to produce bounds on the μ→eJ rate which are comparable with the present ones from direct searches.

  16. Observation of electron excitation into silicon conduction band by slow-ion surface neutralization

    CERN Document Server

    Shchemelinin, S

    2016-01-01

    Bare reverse biased silicon photodiodes were exposed to 3eV He+, Ne+, Ar+, N2+, N+ and H2O+ ions. In all cases an increase of the reverse current through the diode was observed. This effect and its dependence on the ionization energy of the incident ions and on other factors are qualitatively explained in the framework of Auger-type surface neutralization theory. Amplification of the ion-induced charge was observed with an avalanche photodiode under high applied bias. The observed effect can be considered as ion-induced internal potential electron emission into the conduction band of silicon. To the best of our knowledge, no experimental evidence of such effect was previously reported. Possible applications are discussed.

  17. Cascade emission in electron beam ion trap plasma of W$^{25+}$ ion

    CERN Document Server

    Jonauskas, V; Kučas, S; Masys, Š; Kynienė, A; Gaigalas, G; Kisielius, R; Radžiūtė, L; Rynkun, P; Merkelis, G

    2015-01-01

    Spectra of the W$^{25+}$ ion are studied using the collisional-radiative model (CRM) with an ensuing cascade emission. It is determined that the cascade emission boosts intensities only of a few lines in the $10 - 3$ nm range. The cascade emission is responsible for the disappearance of structure of lines at about 6 nm in the electron beam ion trap plasma. Emission band at 4.5 to 5.3 nm is also affected by the cascade emission. The strongest lines in the CRM spectrum correspond to $4d^{9} 4f^{4} \\rightarrow 4f^{3}$ transitions, while $4f^{2} 5d \\rightarrow 4f^{3}$ transitions arise after the cascade emission is taken into account.

  18. The use of field emission scanning electron microscopy to assess recombinant adenovirus stability.

    Science.gov (United States)

    Obenauer-Kutner, Linda J; Ihnat, Peter M; Yang, Tong-Yuan; Dovey-Hartman, Barbara J; Balu, Arthi; Cullen, Constance; Bordens, Ronald W; Grace, Michael J

    2002-09-20

    A field emission scanning electron microscopy (FESEM) method was developed to assess the stability of a recombinant adenovirus (rAd). This method was designed to simultaneously sort, count, and size the total number of rAd viral species observed within an image field. To test the method, a preparation of p53 transgene-expressing recombinant adenovirus (rAd/p53) was incubated at 37 degrees C and the viral particles were evaluated by number, structure, and degree of aggregation as a function of time. Transmission electron microscopy (TEM) was also used to obtain ultrastructural detail. In addition, the infectious activity of the incubated rAd/p53 samples was determined using flow cytometry. FESEM image-analysis revealed that incubation at 37 degrees C resulted in a time-dependent decrease in the total number of detectable single rAd/p53 virus particles and an increase in apparent aggregates composed of more than three adenovirus particles. There was also an observed decrease in both the diameter and perimeter of the single rAd/p53 viral particles. TEM further revealed the accumulation of damaged single particles with time at 37 degrees C. The results of this study demonstrate that FESEM, coupled with sophisticated image analysis, may be an important tool in quantifying the distribution of aggregated species and assessing the overall stability of rAd samples.

  19. Correlative microscopy of Purkinje dendritic spines: a field emission scanning and transmission electron microscopic study.

    Science.gov (United States)

    Castejón, O J; Castellano, A; Arismendi, G; Apkarian, R

    2004-01-01

    Purkinje dendritic spines (Pds) of mouse cerebellar cortex were examined by field emission scanning electron microscopy (FESEM) and by transmission electron microscopy (TEM) using ultrathin sections and freeze-etching replicas, to study their three-dimensional features and intramembrane morphology. FESEM showed unattached mushroom-type, elongated and lanceolate Pds separated by 100-500 nm on the dendritic shaft surface. High resolution FESEM showed 25-50 nm globular subunits at the spine postsynaptic density corresponding to the localization of postsynaptic proteins and/or postsynaptic receptors. TEM images of ultrathin sections showed gem-like, mushroom-shaped, lanceolate and neckless or stubby spines. Freeze etching replicas exposed postsynaptic intramembrane particles that can be correlated with the globular subunits observed at high resolution FESEM. Parallel and climbing fiber endings were observed making asymmetric synaptic contacts with the Pds heads. Simultaneous contacts with the necks and heads were also found. The variety of Pds shapes were interpreted as spine conformational changes related with spine dynamic, and spine plasticity.

  20. Evaluation of the Fast-Electron Source Function for Two-Plasmon Decay from Temporal Hard X-Ray Emission

    Science.gov (United States)

    Delettrez, J. A.; Follett, R. K.; Myatt, J. F.; Stoeckl, C.

    2016-10-01

    The modeling of the fast-electron transport in the 1-D hydrodynamic code LILAC requires the description of the source electrons as a function of time. The particle-in-cell code OSIRIS and the interaction code FPSE provide some guidance but have not provided an algorithm for the energy fraction from the laser pulse as the coronal parameters change with time. The original algorithm, based on the measured hard x-ray (HXR) emission as a function of laser intensity, depended exponentially on the two-plasmon-decay threshold parameter up to about 0.9 and saturates above it. This algorithm along with FPSE simulations produced HXR emissions much earlier than observed. Analysis of the measured HXR emissions from implosions with near-constant threshold parameter values show that the rise time of the emission can be described with an exponential curve with roughly a rise time of 200 ps. Trial and error set the start of the rise at the threshold value of 0.75. Causes for this rise time will be discussed. Comparison between measured and computed HXR emissions for different implosion scenarios will be presented, including those for cryogenic targets. This material is based upon work supported by the Department of Energy National Nuclear Security Administration under Award Number DE-NA0001944.

  1. Shedding new light on thermionic electron emission of fullerenes

    NARCIS (Netherlands)

    von Helden, G.; Holleman, I.; van Roij, A. J. A.; Knippels, G.M.H.; van der Meer, A. F. G.; Meijer, G.

    1998-01-01

    Tunable pulsed infrared (IR) radiation from a free electron laser is used to selectively excite fullerenes via their vibrational modes to very high internal energies. After absorbing several hundred IR photons, the molecules can autoionize. Ion creation is unexpectedly slow, occurring at times

  2. Stochastic Coulomb interactions in space charge limited electron emission

    NARCIS (Netherlands)

    Nijkerk, M.D.; Kruit, P.

    2004-01-01

    A Monte Carlo simulation tool, which was used to evaluate the influence of discrete space charge effects on self-consistent calculations of cathode-ray tube optics, was discussed. It was found that interactions in the space charge cloud affect the electron trajectories such that the velocity

  3. Field-emission cathode gating for rf electron guns

    OpenAIRE

    Lewellen, J. W.; J. Noonan

    2005-01-01

    We present a novel method of combining the most desirable characteristics of thermionic-cathode and photocathode rf guns, using a field-emission cathode and multiple rf frequencies. Simulations indicate that extremely low-emittance beams (on the order of 2 nm normalized emittance) at moderate beam currents (1 mA) and beam energies of ∼2  MeV can be obtained using this technique. The resulting gun design promises to be useful as a driver source for a number of applications, including high-volt...

  4. Thermionic field emission of electrons from the paraboloidal metal micropoint

    Science.gov (United States)

    Petrin, A. B.

    2017-06-01

    The problem of determining the emission current as a function of voltage, radius of the micropoint curvature, and the distance between the micropoint and a conducting plane is considered on the basis of the theoretical method developed for determining the electric field in the vicinity of a paraboloidal micropoint near a plane metal surface. The universal current-voltage characteristics for a copper micropoint, which are considered for various distances between the micropoint and the plane, can be used for obtaining quantitative estimates of currents in various physics problems.

  5. Ion gyro-harmonic structuring in the stimulated radiation spectrum and optical emissions during electron gyro-harmonic heating

    Science.gov (United States)

    Mahmoudian, A.; Scales, W. A.; Bernhardt, P. A.; Samimi, A.; Kendall, E.; Ruohoniemi, J. M.; Isham, B.; Vega-Cancel, O.; Bordikar, M.

    2013-03-01

    Stimulated electromagnetic emissions (SEEs) are secondary radiation produced during active space experiments in which the ionosphere is actively heated with high power high frequency (HF) ground-based radio transmitters. Recently, there has been significant interest in ion gyro-harmonic structuring the SEE spectrum due to the potential for new diagnostic information available such as electron acceleration and creation of artificial ionization layers. These relatively recently discovered gyro-harmonic spectral features have almost exclusively been studied when the transmitting frequency is near the second electron gyro-harmonic frequency. The first extensive systematic experimental investigations of the possibility of these spectral features for third electron gyro-harmonic heating are provided here. Discrete spectral features shifted from the transmit frequency ordered by harmonics of the ion gyro-frequency were observed for third electron gyro-harmonic heating for the first time at a recent campaign at the High Frequency Active Auroral Research Program (HAARP) facility. These features were also closely correlated with a broader band feature at a larger frequency shift from the transmit frequency known as the downshifted peak (DP). The power threshold of these spectral features was measured, as well as their behavior with heater beam angle, and proximity of the transmit frequency to the third electron gyro-harmonic frequency. Comparisons were also made with similar spectral features observed during second electron gyro-harmonic heating during the same campaign. A theoretical model is provided that interprets these spectral features as resulting from parametric decay instabilities in which the pump field ultimately decays into high frequency upper hybrid/electron Bernstein and low frequency neutralized ion Bernstein IB and/or obliquely propagating ion acoustic waves at the upper hybrid interaction altitude. Coordinated optical and SEE observations were carried out

  6. Mechanism of two types of Na emission observed in sonoluminescence

    Science.gov (United States)

    Nakajima, Ryota; Hayashi, Yuichi; Choi, Pak-Kon

    2015-07-01

    The sonoluminescence (SL) spectrum of Na atoms revealed that the Na line consists of two components, one of which is a broadened component (broad component) which is shifted from the original D lines, and the other is an unshifted narrow component (narrow component). We spatially separated the continuum, broad, and narrow components by capturing SL images using different optical filters. We also temporally separated these components by measuring SL pulses using respective band-pass filters. The SL image distribution and the timing of the SL pulses were different between the broad and narrow components. The results suggested that the broad and narrow components of Na emission are generated from different bubble populations. The dependences of SL spectra on ultrasonic frequency and dissolved rare gas (He, Ne, Ar, Kr, and Xe) were also investigated. It is concluded that the broad component and a blue satellite peak at 558 nm originate from van der Waals molecules composed of Na and rare-gas atoms. The narrow component was predicted to occur under temperature conditions at bubble collapse higher than that for the broad component.

  7. 3D Observation of GEMS by Electron Tomography

    Science.gov (United States)

    Matsuno, Junya; Miyake, Akira; Tsuchiyama, Akira; Nakamura-Messenger, Keiko; Messenger, Scott

    2014-01-01

    Amorphous silicates in chondritic porous interplanetary dust particles (CP-IDPs) coming from comets are dominated by glass with embedded metal and sulfides (GEMS). GEMS grains are submicron-sized rounded objects (typically 100-500) nm in diameter) with anaometer-sized (10-50 nm) Fe-Ni metal and sulfide grains embedded in an amorphous silicate matrix. Several formation processes for GEMS grains have been proposed so far, but these models are still being debated [2-5]. Bradley et al. proposed that GEMS grains are interstellar silicate dust that survived various metamorphism or alteration processes in the protoplanetary disk and that they are amorphiation products of crystalline silicates in the interstellar medium by sputter-deposition of cosmic ray irradiation, similar to space weathering [2,4]. This consideration is based on the observation of nano-sized crystals (approximately 10 nm) called relict grains in GEMS grains and their shapes are pseudomorphs to the host GEMS grains. On the other hand, Keller and Messenger proposed that most GEMS formed in the protoplanetary disk as condensates from high temperature gas [3,5]. This model is based on the fact that most GEMS grains have solar isotopic compositions and have extremely heterogeneous and non-solar elemental compositions. Keller and Messenger (2011) also reported that amorphous silicates in GEMS grains are surrounded by sulfide grains, which formed as sulfidization of metallic iron grains located on the GEMS surface. The previous studies were performed with 2D observation by using transmission electron microscopy (TEM) or scanning TEM (STEM). In order to understand the structure of GEMS grains described above more clearly, we observed 3D structure of GEMS grains by electron tomography using a TEM/STEM (JEM-2100F, JEOL) at Kyoto University. Electron tomography gives not only 3D structures but also gives higher spatial resolution (approximately a few nm) than that in conventional 2D image, which is restricted by

  8. Plasma-Wall Interaction with Strong Electron Emission Revisited

    Science.gov (United States)

    Campanell, Michael

    2016-10-01

    Half a century ago, Hobbs and Wesson derived a solution for the plasma sheath at a planar surface with emission coefficient γ. They predicted that the floating sheath potential remains negative when γ >1. Variations of their ``space-charge limited'' (SCL) sheath model have long been used to estimate the particle and energy fluxes at strongly emitting surfaces. Recent theory, simulation and experimental studies show that another plasma-wall equilibrium is possible when γ >1. In the ``inverse regime'', the sheath potential is positive, repelling ions from the wall. The quasineutral density gradient and force balance in the ``inverted presheath'' are much different from the Bohm presheaths contained in the SCL models. It turns out that a SCL plasma-wall equilibrium is only stable under the assumption of zero ionization inside the sheath. Otherwise, the cumulative trapping of new ions in the SCL's potential ``dip'' will force a transition to the inverse regime. It follows that only an inverse equilibrium should be possible in practice at floating surfaces with strong secondary, thermionic or photoelectron emissions. Applications will be discussed. This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract No. DE-AC52-07NA27344.

  9. Electron dynamics in RF sources with a laser controlled emission

    CERN Document Server

    Khodak, I V; Metrochenko, V V

    2001-01-01

    Photoemission radiofrequency (RF) electron sources are sources of electron beams with extremely high brightness. Beam bunching processes in such devices are well studied in case when laser pulse duration is much lower of rf oscillation period.At the same time photoemission RF guns have some merits when operating in 'long-pulse' mode. In this case the laser pulse duration is much higher of rf oscillation period but much lower of rise time of oscillations in a gun cavity. Beam parameters at the gun output are compared for photoemission and thermoemission cathode applications. The paper presents results of a beam dynamics simulation in such guns with different resonance structures. Questions connected with defining of the current pulse peak value that can be obtained in such guns are discussed.

  10. Dynamics of energetic electrons interacting with sub-packet chorus emissions in the magnetosphere

    Science.gov (United States)

    Hiraga, R.; Omura, Y.

    2016-12-01

    The recent study has revealed RTA and URA processes, the acceleration of relativistic electrons by interaction with chorus emissions. The wave model, however, is found to require some updates based on the recent observations. We develop a new wave model compatible with the observations and study the particle motion under the influence of this new wave model. The most distinctive feature of the new model is its amplitude growth manner. The wave is excited near the equator and grows in amplitude as an absolute instability as a function of time. This amplitude growth is bounded by the optimum and threshold amplitudes. When the amplitude grows to reach the optimum amplitude, it drops down to the threshold value and repeats the growth with a saw-like shape defined as sub-packet wave. The sub-packet wave generated near the equator experiences the convective amplitude growth propagating to the higher latitude region. Since the group velocity of the wave propagation is a function of its frequency, a wave source generated and released from the equator at a certain time and a group velocity could be overtaken by another wave released at a later timing and hence a faster group velocity. In sub-packet case, this frequency value is further affected by the sub-packet amplitude wave form to make the process more complex. Into this new wave form, energetic electrons are inserted and their motions are examined. For example, a resonant electron can be entrapped by the wave, being accelerated and normally detrapped after a certain period of time, but there can be a possibility that the following sub-packet wave in a complex propagation manner coincidently entraps the electron to provide multiple accelerations. We injected a large number of electrons over a wide energy range from 10kev to 10Mev into the sub-packet wave to simulate the nonlinear dynamics of RTA and URA. The electrons motion or more precisely entrapping and detrapping processes are examined under various conditions.

  11. Obtaining attosecond x-ray pulses using a self-amplified spontaneous emission free electron laser

    Directory of Open Access Journals (Sweden)

    A. A. Zholents

    2005-05-01

    Full Text Available We describe a technique for the generation of a solitary attosecond x-ray pulse in a free-electron laser (FEL, via a process of self-amplified spontaneous emission. In this method, electrons experience an energy modulation upon interacting with laser pulses having a duration of a few cycles within single-period wiggler magnets. Two consecutive modulation sections, followed by compression in a dispersive section, are used to obtain a single, subfemtosecond spike in the electron peak current. This region of the electron beam experiences an enhanced growth rate for FEL amplification. After propagation through a long undulator, this current spike emits a ∼250   attosecond x-ray pulse whose intensity dominates the x-ray emission from the rest of the electron bunch.

  12. Observation of electron-antineutrino disappearance at Daya Bay

    CERN Document Server

    An, F P; Balantekin, A B; Band, H R; Beavis, D; Beriguete, W; Bishai, M; Blyth, S; Brown, R L; Cao, G F; Cao, J; Carr, R; Chan, W T; Chang, J F; Chang, Y; Chasman, C; Chen, H S; Chen, H Y; Chen, S J; Chen, S M; Chen, X C; Chen, X H; Chen, X S; Chen, Y; Chen, Y X; Cherwinka, J J; Chu, M C; Cummings, J P; Deng, Z Y; Ding, Y Y; Diwan, M V; Dong, L; Draeger, E; Du, X F; Dwyer, D A; Edwards, W R; Ely, S R; Fang, S D; Fu, J Y; Fu, Z W; Ge, L Q; Ghazikhanian, V; Gill, R L; Goett, J; Gonchar, M; Gong, G H; Gong, H; Gornushkin, Y A; Greenler, L S; Gu, W Q; Guan, M Y; Guo, X H; Hackenburg, R W; Hahn, R L; Hans, S; He, M; He, Q; He, W S; Heeger, K M; Heng, Y K; Hinrichs, P; Ho, T H; Hor, Y K; Hsiung, Y B; Hu, B Z; Hu, T; Hu, T; Huang, H X; Huang, H Z; Huang, P W; Huang, X; Huang, X T; Huber, P; Isvan, Z; Jaffe, D E; Jetter, S; Ji, X L; Ji, X P; Jiang, H J; Jiang, W Q; Jiao, J B; Johnson, R A; Kang, L; Kettell, S H; Kramer, M; Kwan, K K; Kwok, M W; Kwok, T; Lai, C Y; Lai, W C; Lai, W H; Lau, K; Lebanowski, L; Lee, J; Lee, M K P; Leitner, R; Leung, J K C; Leung, K Y; Lewis, C A; Li, B; Li, F; Li, G S; Li, J; Li, Q J; Li, S F; Li, W D; Li, X B; Li, X N; Li, X Q; Li, Y; Li, Z B; Liang, H; Liang, J; Lin, C J; Lin, G L; Lin, S K; Lin, S X; Lin, Y C; Ling, J J; Link, J M; Littenberg, L; Littlejohn, B R; Liu, B J; Liu, C; Liu, D W; Liu, H; Liu, J C; Liu, J L; Liu, S; Liu, X; Liu, Y B; Lu, C; Lu, H Q; Luk, A; Luk, K B; Luo, T; Luo, X L; Ma, L H; Ma, Q M; Ma, X B; Ma, X Y; Ma, Y Q; Mayes, B; McDonald, K T; McFarlane, M C; McKeown, R D; Meng, Y; Mohapatra, D; Morgan, J E; Nakajima, Y; Napolitano, J; Naumov, D; Nemchenok, I; Newsom, C; Ngai, H Y; Ngai, W K; Nie, Y B; Ning, Z; Ochoa-Ricoux, J P; Olshevski, A; Pagac, A; Patton, S; Pearson, C; Pec, V; Peng, J C; Piilonen, L E; Pinsky, L; Pun, C S J; Qi, F Z; Qi, M; Qian, X; Raper, N; Rosero, R; Roskovec, B; Ruan, X C; Seilhan, B; Shao, B B; Shih, K; Steiner, H; Stoler, P; Sun, G X; Sun, J L; Tam, Y H; Tanaka, H K; Tang, X; Themann, H; Torun, Y; Trentalange, S; Tsai, O; Tsang, K V; Tsang, R H M; Tull, C; Viren, B; Virostek, S; Vorobel, V; Wang, C H; Wang, L S; Wang, L Y; Wang, L Z; Wang, M; Wang, N Y; Wang, R G; Wang, T; Wang, W; Wang, X; Wang, X; Wang, Y F; Wang, Z; Wang, Z; Wang, Z M; Webber, D M; Wei, Y D; Wen, L J; Wenman, D L; Whisnant, K; White, C G; Whitehead, L; Whitten, C A; Wilhelmi, J; Wise, T; Wong, H C; Wong, H L H; Wong, J; Worcester, E T; Wu, F F; Wu, Q; Xia, D M; Xiang, S T; Xiao, Q; Xing, Z Z; Xu, G; Xu, J; Xu, J; Xu, J L; Xu, W; Xu, Y; Xue, T; Yang, C G; Yang, L; Ye, M; Yeh, M; Yeh, Y S; Yip, K; Young, B L; Yu, Z Y; Zhan, L; Zhang, C; Zhang, F H; Zhang, J W; Zhang, Q M; Zhang, K; Zhang, Q X; Zhang, S H; Zhang, Y C; Zhang, Y H; Zhang, Y X; Zhang, Z J; Zhang, Z P; Zhang, Z Y; Zhao, J; Zhao, Q W; Zhao, Y B; Zheng, L; Zhong, W L; Zhou, L; Zhou, Z Y; Zhuang, H L; Zou, J H

    2012-01-01

    The Daya Bay Reactor Neutrino Experiment has measured a non-zero value for the neutrino mixing angle $\\theta_{13}$ with a significance of 5.2 standard deviations. Antineutrinos from six 2.9 GW$_{\\rm th}$ reactors were detected in six antineutrino detectors deployed in two near (flux-weighted baseline 470 m and 576 m) and one far (1648 m) underground experimental halls. With 55 days of data, 10416 (80376) electron antineutrino candidates were detected at the far hall (near halls). The ratio of the observed to expected number of antineutrinos at the far hall is $R=0.940\\pm 0.011({\\rm stat}) \\pm 0.004({\\rm syst})$. A rate-only analysis finds $\\sin^22\\theta_{13}=0.092\\pm 0.016({\\rm stat})\\pm0.005({\\rm syst})$ in a three-neutrino framework.

  13. CLUSTER observations of electron outflowing beams carrying downward currents above the polar cap by northward IMF

    Directory of Open Access Journals (Sweden)

    A. Teste

    2007-05-01

    Full Text Available Above the polar cap, at about 5–9 Earth radii (RE altitude, the PEACE experiment onboard CLUSTER detected, for the first time, electron beams outflowing from the ionosphere with large and variable energy fluxes, well collimated along the magnetic field lines. All these events occurred during periods of northward or weak interplanetary magnetic field (IMF.

    These outflowing beams were generally detected below 100 eV and typically between 40 and 70 eV, just above the photoelectron level. Their energy gain can be explained by the presence of a field-aligned potential drop below the spacecraft, as in the auroral zone. The careful analysis of the beams distribution function indicates that they were not only accelerated but also heated. The parallel heating is estimated to about 2 to 20 eV and it globally tends to increase with the acceleration energy. Moreover, WHISPER observed broadband electrostatic emissions around a few kHz correlated with the outflowing electron beams, which suggests beam-plasma interactions capable of triggering plasma instabilities.

    In presence of simultaneous very weak ion fluxes, the outflowing electron beams are the main carriers of downward field-aligned currents estimated to about 10 nA/m2. These electron beams are actually not isolated but surrounded by wider structures of ion outflows. All along its polar cap crossings, Cluster observed successive electron and ion outflows. This implies that the polar ionosphere represents a significant source of cold plasma for the magnetosphere during northward or weak IMF conditions. The successive ion and electron outflows finally result in a filamented current system of opposite polarities which connects the polar ionosphere to distant regions of the magnetosphere.

  14. CLUSTER observations of electron outflowing beams carrying downward currents above the polar cap by northward IMF

    Directory of Open Access Journals (Sweden)

    A. Teste

    2007-05-01

    Full Text Available Above the polar cap, at about 5–9 Earth radii (RE altitude, the PEACE experiment onboard CLUSTER detected, for the first time, electron beams outflowing from the ionosphere with large and variable energy fluxes, well collimated along the magnetic field lines. All these events occurred during periods of northward or weak interplanetary magnetic field (IMF. These outflowing beams were generally detected below 100 eV and typically between 40 and 70 eV, just above the photoelectron level. Their energy gain can be explained by the presence of a field-aligned potential drop below the spacecraft, as in the auroral zone. The careful analysis of the beams distribution function indicates that they were not only accelerated but also heated. The parallel heating is estimated to about 2 to 20 eV and it globally tends to increase with the acceleration energy. Moreover, WHISPER observed broadband electrostatic emissions around a few kHz correlated with the outflowing electron beams, which suggests beam-plasma interactions capable of triggering plasma instabilities. In presence of simultaneous very weak ion fluxes, the outflowing electron beams are the main carriers of downward field-aligned currents estimated to about 10 nA/m2. These electron beams are actually not isolated but surrounded by wider structures of ion outflows. All along its polar cap crossings, Cluster observed successive electron and ion outflows. This implies that the polar ionosphere represents a significant source of cold plasma for the magnetosphere during northward or weak IMF conditions. The successive ion and electron outflows finally result in a filamented current system of opposite polarities which connects the polar ionosphere to distant regions of the magnetosphere.

  15. Emission Flux Measurement Error with a Mobile DOAS System and Application to NOx Flux Observations.

    Science.gov (United States)

    Wu, Fengcheng; Li, Ang; Xie, Pinhua; Chen, Hao; Hu, Zhaokun; Zhang, Qiong; Liu, Jianguo; Liu, Wenqing

    2017-01-25

    Mobile differential optical absorption spectroscopy (mobile DOAS) is an optical remote sensing method that can rapidly measure trace gas emission flux from air pollution sources (such as power plants, industrial areas, and cities) in real time. Generally, mobile DOAS is influenced by wind, drive velocity, and other factors, especially in the usage of wind field when the emission flux in a mobile DOAS system is observed. This paper presents a detailed error analysis and NOx emission with mobile DOAS system from a power plant in Shijiazhuang city, China. Comparison of the SO₂ emission flux from mobile DOAS observations with continuous emission monitoring system (CEMS) under different drive speeds and wind fields revealed that the optimal drive velocity is 30-40 km/h, and the wind field at plume height is selected when mobile DOAS observations are performed. In addition, the total errors of SO₂ and NO₂ emissions with mobile DOAS measurements are 32% and 30%, respectively, combined with the analysis of the uncertainties of column density, wind field, and drive velocity. Furthermore, the NOx emission of 0.15 ± 0.06 kg/s from the power plant is estimated, which is in good agreement with that from CEMS observations of 0.17 ± 0.07 kg/s. This study has significantly contributed to the measurement of the mobile DOAS system on emission from air pollution sources, thus improving estimation accuracy.

  16. Secondary electron emission characteristics of molybdenum-masked, ion-textured OFHC copper

    Science.gov (United States)

    Curren, Arthur N.; Jensen, Kenneth A.; Roman, Robert F.

    1990-01-01

    A method for producing a uniform, highly textured surface on oxygen-free, high conductivity (OFHC) copper by ion bombardment using sputtered molybdenum as a texture-inducing masking film was developed and used to provide samples for study. The purpose was to develop a basically OFHC copper surface having very low secondary electron emission characteristics. Surfaces having low secondary electron emission are a requirement for the electrodes of very high efficiency multistage depressed collectors (MDC's). Such MDC's are used in microwave amplifier traveling wave tubes for space communications and other applications. OFHC copper is the material most commonly used for MDC electrodes because it has high thermal conductivity, it is easy to machine, and its fabrication and brazing procedures are well established. However, its untreated surface displays relatively very high levels of secondary electron emissions. Textured OFHC copper samples were tested for true secondary electron emission and relative reflected primary electron yield at primary electron beam energy levels from 200 to 2000 eV and at direct (0 deg) to oblique (60 deg) beam impingement angles. The test results for three of the samples, each of which was processed in a slightly different way, are compared with each other and with test results for a machined OFHC copper sample. Although the textured samples are not represented here as having been processed optimally, their measured secondary electron emission characteristics are significantly lower than those of the untreated OFHC copper sample over the range of conditions studied. Importantly, the relative reflected primary electron yield of one of the textured samples is conspicuously lower than that of the others. Clearly, with further development, the molybdenum-masked ion-textured OFHC copper surface will be a promising material for high-efficiency MDC electrodes.

  17. Environmental scanning electron microscopy observation of the ultrastructure of Demodex.

    Science.gov (United States)

    Jing, Xu; Shuling, Guo; Ying, Liu

    2005-12-01

    In this study, numbers of Demodex of hair follicles and sebaceous glands were prepared and the ultrastructure (especially the mouthparts) of Demodex was observed firstly with environmental scanning electron microscopy (ESEM). The most suitable treatment methods and optimal environmental condition for observing the genus samples were found. The samples were washed with detergent and rinsed with distilled water, and then were taken to the specimen stage, on which there was carbon adhesive tape, using special tools. When the temperature was at 5 degrees C and chamber pressure at 5 mbar respectively, the surface of the samples could be fully imaged without covering water or dehydration. The sample surfaces were plump and clear without postmortem changes and charging artifacts. Detailed information about each part of Demodex was observed by ESEM, and clear three-dimensional images were recorded. The mouthparts of D. folliculorum were composed of a complex set of structures, which included a round oral opening, a sharp oral needle, and a special hypostome that looked like a longitudinal spindle in the central position. On the end segment of palpus, there were seven strong palpal claws located on each side of the mouthparts. D. folliculorum had special piercing mouthparts, while the mouthparts of D. brevis were a simpler structure. We could not observe the oral needle of D. brevis, and there were only five pairs of palpal claws on the end segment of palpus. The offensive organs of Demodex resulted in its pathogenic effects. After studying hundreds of Demodex, we identified both female and male species of D. folliculorum, but only females of D. brevis in our sample. (c) 2005 Wiley-Liss, Inc.

  18. Measuring the Density of a Molecular Cluster Injector via Visible Emission from an Electron Beam

    Energy Technology Data Exchange (ETDEWEB)

    Lundberg, D. P.; Kaita, R.; Majeski, R. M.; Stotler, D. P.

    2010-06-28

    A method to measure the density distribution of a dense hydrogen gas jet is pre- sented. A Mach 5.5 nozzle is cooled to 80K to form a flow capable of molecular cluster formation. A 250V, 10mA electron beam collides with the jet and produces Hα emission that is viewed by a fast camera. The high density of the jet, several 1016cm-3, results in substantial electron depletion, which attenuates the Hα emission. The attenuated emission measurement, combined with a simplified electron-molecule collision model, allows us to determine the molecular density profile via a simple iterative calculation.

  19. Exponential gain and saturation of a self-amplified spontaneous emission free-electron laser.

    Science.gov (United States)

    Milton, S V; Gluskin, E; Arnold, N D; Benson, C; Berg, W; Biedron, S G; Borland, M; Chae, Y C; Dejus, R J; Den Hartog, P K; Deriy, B; Erdmann, M; Eidelman, Y I; Hahne, M W; Huang, Z; Kim, K J; Lewellen, J W; Li, Y; Lumpkin, A H; Makarov, O; Moog, E R; Nassiri, A; Sajaev, V; Soliday, R; Tieman, B J; Trakhtenberg, E M; Travish, G; Vasserman, I B; Vinokurov, N A; Wang, X J; Wiemerslage, G; Yang, B X

    2001-06-15

    Self-amplified spontaneous emission in a free-electron laser has been proposed for the generation of very high brightness coherent x-rays. This process involves passing a high-energy, high-charge, short-pulse, low-energy-spread, and low-emittance electron beam through the periodic magnetic field of a long series of high-quality undulator magnets. The radiation produced grows exponentially in intensity until it reaches a saturation point. We report on the demonstration of self-amplified spontaneous emission gain, exponential growth, and saturation at visible (530 nanometers) and ultraviolet (385 nanometers) wavelengths. Good agreement between theory and simulation indicates that scaling to much shorter wavelengths may be possible. These results confirm the physics behind the self-amplified spontaneous emission process and forward the development of an operational x-ray free-electron laser.

  20. Discovery of electron cyclotron MASER emission from the magnetic Bp star HD 133880 with the Giant Metrewave Radio Telescope

    Science.gov (United States)

    Das, Barnali; Chandra, Poonam; Wade, Gregg A.

    2018-02-01

    We report the discovery of coherent radio emission from the young, rapidly rotating magnetic Bp star HD 133880 at a frequency of 610 MHz with the Giant Metrewave Radio Telescope (GMRT). This is only the second magnetic star in which coherent radio emission has been detected. In our observations of HD 133880 covering the full rotational cycle of the star (except for a phase window 0.17-0.24), we witness an abrupt order-of-magnitude flux enhancement along with ≈100 per cent right circular polarization. We attribute this phenomenon to coherent electron cyclotron MASER emission. We attribute the lack of left circularly polarized emission to the asymmetric topology of the star's magnetic field. The phase of enhancement, 0.73, differs from the previously reported phase of enhancement, 0.16, (at 610 MHz)by one-half cycle. However, no flux enhancement is found at phase 0.16 in our data, which could be due to an unstable or drifting emission region, or a consequence of the reported changes of the star's rotational period. Either of these factors could have shifted the enhancement to the above-mentioned phase window not sampled by our observations.

  1. Energy loss and electron and x-ray emission of slow highly charged Arq+ ions in grazing incidence on an Al(111) surface

    Science.gov (United States)

    Luo, Xianwen; Hu, Bitao; Zhang, Chengjun; Wang, Jijin; Chen, Chunhua

    2010-05-01

    Within the framework of the classical over-barrier model, energy loss, electron emission, and x-ray emission of slow highly charged ion Arq+ grazing on the Al(111) single-crystal surface under various azimuthal angles have been studied. The enhancement of energy loss, potential electron emission yields, intensity of KL1 satellite lines, or x-ray yields for the Ar17+ ion grazing along low-index crystallographic directions was observed. The calculated energy-loss spectra of atomic projectiles Ar0 interacting with metallic surface agree reasonably well with experiment. The inner-shell filling contributions through the side feeding mechanism, Auger transitions, and the radiative decay process are discussed by analyzing the final charge-state distributions of the reflected ions, potential electron emission yields, and x-ray yields under different azimuthal angles.

  2. Coherence and partial localization in electron emission from asymmetric diatomic molecules

    Energy Technology Data Exchange (ETDEWEB)

    Tachino, C A; Galassi, M E; Rivarola, R D [Instituto de Fisica Rosario, Consejo Nacional de Investigaciones Cientificas y Tecnicas, Universidad Nacional de Rosario, Av. Pellegrini 250, 2000 Rosario (Argentina); Martin, F, E-mail: rivarola@fceia.unr.edu.ar [Departamento de Quimica, C-9, Universidad Autonoma de Madrid, 28049 Madrid (Spain)

    2011-04-01

    The presence of interference patterns in the spectra of emitted electrons from HeH{sup +} molecular ions due to the impact of bare ions is analysed. It is shown that these oscillations, which are explained in terms of the coherent emission of electrons from the vicinities of the target nuclei, are preserved even after averaging over all molecular orientations. The influence of partial localization of electrons around the alpha particle center is studied. The relationship between electron ionization by ion impact and photoionization is investigated.

  3. Ground pulsation magnetometer observations conjugated with relativistic electron precipitation

    Science.gov (United States)

    Yahnin, A. G.; Yahnina, T. A.; Raita, T.; Manninen, J.

    2017-09-01

    In this report, we investigate the role of electromagnetic ion cyclotron (EMIC) waves in production of relativistic electron precipitation (REP). Over a thousand REP events were detected from four NOAA Polar-orbiting Operational Environmental Satellites in July-December 2005. Of these, a total of 112 events were conjugated with a ground-based network of six Finnish induction coil magnetometers and one in Lovozero observatory at Kola Peninsula, Russia. The observation of geomagnetic pulsations during the conjugated events showed that about one third of them were accompanied by pulsations in the Pc1 range, which are the signature of EMIC waves. In fact, the sources of some of these EMIC waves were well outside the location of the REP event. This means that in such cases the REP events were not originated from scattering by EMIC waves. Finally, it is concluded that for this limited set of conjugated events only a quarter might be related to scattering by EMIC waves. The majority of the events are not correlated with EMIC wave signatures in ground-based observations; they were associated with either no pulsations or noise-like pulsations PiB and PiC.

  4. Kinetic Features Observed in the Solar Wind Electron Distributions

    Science.gov (United States)

    Pierrard, V.; Lazar, M.; Poedts, S.

    2016-12-01

    More than 120 000 of velocity distributions measured by Helios, Cluster and Ulysses in the ecliptic have been analyzed within an extended range of heliocentric distances from 0.3 to over 4 AU. The velocity distribution of electrons reveal a dual structure with a thermal (Maxwellian) core and a suprathermal (Kappa) halo. A detailed observational analysis of these two components provides estimations of their temperatures and temperature anisotropies, and we decode any potential interdependence that their properties may indicate. The core temperature is found to decrease with the radial distance, while the halo temperature slightly increases, clarifying an apparent contradiction in previous observational analysis and providing valuable clues about the temperature of the Kappa-distributed populations. For low values of the power-index kappa, these two components manifest a clear tendency to deviate from isotropy in the same direction, that seems to confirm the existence of mechanisms with similar effects on both components, e.g., the solar wind expansion, or the particle heating by the fluctuations. However, the existence of plasma states with anti-correlated anisotropies of the core and halo populations and the increase of their number for high values of the power-index kappa suggest a dynamic interplay of these components, mediated most probably by the anisotropy-driven instabilities. Estimating the temperature of the solar wind particles and their anisotropies is particularly important for understanding the origin of these deviations from thermal equilibrium as well as their effects.

  5. First direct observation of runaway electron-driven whistler waves in tokamaks

    Science.gov (United States)

    Spong, Donald A.

    2017-10-01

    Whistlers are electromagnetic waves that can be driven unstable by energetic electrons and are observed in natural plasmas, such as the ionosphere and Van Allen belts. Recent DIII-D experiments at low density demonstrate the first direct observation of whistlers in tokamaks, with 100-200 MHz waves excited by runaway electrons (REs) in the multi-MeV range. Whistler activity is correlated with RE intensity and the frequencies scale with magnetic field strength and electron density consistent with a whistler dispersion relation. Fluctuations occur in discrete frequency bands, and not a continuum as would be expected from plane wave analysis, suggesting the important role of toroidicity. An MHD model including the bounded/periodic nature of the plasma identifies multiple eigenmode branches. For a toroidal mode number n = 10, the predicted frequencies and spacing are similar to observations. The instabilities are stabilized with increasing magnetic field, as expected from the anomalous Doppler resonance. The whistler amplitudes show intermittent time variations. Predator-prey cycles with electron cyclotron emission (ECE) signals are observed, which can be interpreted as wave-induced pitch angle scattering of moderate energy REs. Such nonlinear dynamics are supported by quasi-linear simulations indicating that REs are scattered both by whistlers and high frequency magnetized plasma waves. The whistler wave predominantly scatters the high energy REs, while the magnetized plasma wave scatters the low energy REs, abruptly enhancing the ECE signal. Amplitude variations are also associated with sawtooth activity, indicating that the REs sample the q = 1 surface. These features of the RE-driven whistler have connections to ionospheric plasmas and open up new directions for the modeling and active control of tokamak REs. Work supported by the US DOE under DE-FC02-04ER54698, DE-AC52-07NA27344, DE-FG02-07ER54917, DE-SC00-16268, and DE-AC05-00OR22725.

  6. On ion gyro-harmonic structuring in the stimulated electromagnetic emission spectrum during second electron gyro-harmonic heating

    Science.gov (United States)

    Samimi, A.; Scales, W. A.; Bernhardt, P. A.; Briczinski, S. J.; Selcher, C. A.; McCarrick, M. J.

    2012-11-01

    Recent observations show that, during ionospheric heating experiments at frequencies near the second electron gyro-harmonic, discrete spectral lines separated by harmonics of the ion-gyro frequency appear in the stimulated electromagnetic emission (SEE) spectrum within 1 kHz of the pump frequency. In addition to the ion gyro-harmonic structures, on occasion, a broadband downshifted emission is observed simultaneously with these spectral lines. Parametric decay of the pump field into upper hybrid/electron Bernstein (UH/EB) and low-frequency ion Bernstein (IB) and oblique ion acoustic (IA) modes is considered responsible for generation of these spectral features. Guided by predictions of an analytical model, a two-dimensional particle-in-cell (PIC) computational model is employed to study the nonlinear processes during such heating experiments. The critical parameters that affect the spectrum, such as whether discrete gyro-harmonic on broadband structures is observed, include angle of the pump field relative to the background magnetic field, pump field strength, and proximity of the pump frequency to the gyro-harmonic. Significant electron heating along the magnetic field is observed in the parameter regimes considered.

  7. Emission of low-energetic electrons in collisions of heavy ions with solid targets; Emission niederenergetischer Elektronen in Stoessen von schweren Ionen mit Festkoerpertargets

    Energy Technology Data Exchange (ETDEWEB)

    Lineva, Natallia

    2008-07-15

    At the UNILAC accelerator, we have initiated a project with the objective to investigate lowenergy electrons, emitted from solid, electrically conductive targets after the impact of swift light and heavy ions. For this purposes, we have installed, optimized, and put into operation an electrostatic toroidal electron spectrometer. First, investigations of electrons, emitted from solid-state targets after the bombardment with a monochromatic electron beam from an electron gun, has been carried out. The proposed method combines the results of the measurements with the results of dedicated Monte Carlo simulations. The method has been elaborated in a case study for carbon targets. The findings have been instrumental for the interpretation of our measurements of electrons emitted in collisions of swift ions with the same carbon targets. Our investigations focused on following ion beams: protons and (H{sup +}{sub 3})-molecules of the same energy, as well as on carbon ions with two different energies. Thin carbon, nickel, argon and gold foils has been used as targets. Electrons in the energy range between 50 eV and 1 keV have been investigated. The measured electron distributions, both integral as well as differential with respect to the polar angle, have been compared to simple standard theories for gases as well as to the results of TRAX simulations, the latter being based on data from gaseous targets. Dedicated TRAX simulations have been performed only for the carbon targets, applying the method mentioned above. Within our experimental uncertainties, we observe a good agreement of the measured and TRAX simulated data. That leads us to the conclusion that - as a first order approximation - the electron emission pattern from ion-atom collisions in solid-state targets and the one from single collisions in gases are similar. (orig.)

  8. Thermionic and Photo-excited Electron Emission for Energy Conversion Processes

    Directory of Open Access Journals (Sweden)

    Patrick T. McCarthy

    2014-12-01

    Full Text Available This article describes advances in thermionic and photoemission materials and applications dating back to the work on thermionic emission by Guthrie in 1873 and the photoelectric effect by Hertz in 1887. Thermionic emission has been employed for electron beam generation from Edison’s work with the light bulb to modern day technologies such as scanning and transmission electron microscopy. The photoelectric effect has been utilized in common devices such as cameras and photocopiers while photovoltaic cells continue to be widely successful and further researched. Limitations in device efficiency and materials have thus far restricted large-scale energy generation sources based on thermionic and photoemission. However, recent advances in the fabrication of nanoscale emitters suggest promising routes for improving both thermionic and photo-enhanced electron emission along with newly developed research concepts, e.g., photonically enhanced thermionic emission. However, the abundance of new emitter materials and reduced dimensions of some nanoscale emitters increases the complexity of electron emission theory and engender new questions related to the dimensionality of the emitter. This work presents derivations of basic two and three-dimensional thermionic and photoemission theory along with comparisons to experimentally acquired data. The resulting theory can be applied to many different material types regardless of composition, bulk and surface structure.

  9. Observations of soft X-ray emission and plasma dynamics of a compact capillary discharge operated in xenon

    Energy Technology Data Exchange (ETDEWEB)

    Valenzuela, J. C.; Wyndham, E. S.; Favre, M.; Chuaqui, H. [Facultad de Física, Pontificia Universidad Católica de Chile, Av. Vicuña Mackenna 4860, Macul, Santiago (Chile)

    2013-09-15

    We report observations of a low stored energy, low inductance compact capillary discharge operated in xenon. Even though the stored electrical energy is less than 1 J, significant output in the optical windows at 110 and 135 Å is measured. The soft X-ray emission is time-resolved and the conversion energy of the source is obtained. A lower bound to the conversion efficiency at 110 Å ± 2% and 135 Å ± 1% of 3.6% and 1.6% is obtained, respectively. The use of moiré-schlieren optical diagnostic allows the evolution of the line electron density. In particular, we observe a significant degree of compression in a tight on axis pinch as well as radial compression waves. The temporal evolution of the X-ray emission, which occurs during the current reversal and later, is discussed in relation to work in argon discharges and in relation to model calculations.

  10. Electron Emission from Nano and Microstructured Materials for Fusion and Plasma Discharge Applications

    Science.gov (United States)

    Patino, Marlene; Raitses, Yevgeny; Wirz, Richard

    2016-10-01

    Secondary electron emission (SEE) from plasma-facing walls can lead to adverse effects (e.g. increased plasma heat flux to the wall) in plasma devices, including plasma processing, confinement fusion, and plasma thrusters. Experimental and computational efforts of engineered materials with nm to mm-sized structures (grooves, pores, fibers) have previously shown a decrease in SEE for primary electrons incident normal and oblique to the material. Here we present SEE measurements from one such engineered material, carbon velvet with μm fibers, and from a plasma-structured material, tungsten fuzz with nm fibers. Results show two trends: (a) significant reduction in SEE at normal incidence for carbon velvet (75% reduction) and tungsten fuzz (40-50% reduction) over smooth graphite and tungsten, respectively, and (b) SEE from tungsten fuzz is nearly independent of incident angle (i.e. not a cosine dependence on incident angle observed for smooth materials). Hence, the reduction in SEE from tungsten fuzz over smooth tungsten is more pronounced (up to 63%) at grazing angles. This is important for many plasma devices since in a negative-going sheath the potential structure leads to relatively high incident angles. This work was supported by DOE contract DE-AC02-09CH11466; AFOSR Grants FA9550-14-1-0053, FA9550-11-1-0282, AF9550-09-1-0695, and FA9550-14-10317; and DOE Office of Science Graduate Student Research Program.

  11. Cryo-field emission scanning electron microscopy imaging of a rigid surfactant mesophase.

    Science.gov (United States)

    Tan, Grace; Xu, Peng; John, Vijay T; He, Jibao; McPherson, Gary L; Agarwal, Vivek; Bose, Arijit

    2008-10-07

    The aerosol OT/ L-alpha-phosphatidylcholine/isooctane/water system forms a rigid mesophase that transitions from reverse hexagonal to multilamellar in structure at specific water contents. This study shows that characteristics of ordered liquid-crystalline mesophases can be distinguished and imaged in high clarity using cryo-field emission scanning electron microscopy (cryo-FESEM). The reverse hexagonal phase consists of bundles of long cylinders, some with length scales of over 2 microm, that are randomly oriented as part of a larger domain. Cryo-imaging allows the visualization of the intercylinder spacings and the details of transitions from one domain to another. The multilamellar structured mesophase consists of spherical vesicles of 100 nm to 10 microm in diameter, with intervening noncrystalline isotropic regions. Coexistence regions containing both the reverse hexagonal and lamellar structures are also observed in the transition from the reverse hexagonal to the lamellar phase. These results complement and qualitatively verify our earlier studies with small-angle neutron scattering, high-field nuclear magnetic resonance spectroscopy, and freeze-fracture direct imaging transmission electron microscopy. The information is useful in understanding materials templating in these rigid systems.

  12. Design of the 2D electron cyclotron emission imaging instrument for the J-TEXT tokamak

    Energy Technology Data Exchange (ETDEWEB)

    Pan, X. M.; Yang, Z. J., E-mail: yangzj@hust.edu.cn; Ma, X. D.; Ruan, B. W.; Zhuang, G. [State Key Laboratory of Advanced Electromagnetic Engineering and Technology, Huazhong University of Science and Technology, Wuhan, Hubei 430074 (China); Zhu, Y. L. [School of Physics, University of Science and Technology of China, Anhui 230026 (China); Luhmann, N. C.; Domier, C. W. [Davis Millimeter Wave Research Center, University of California, Davis, California 95616 (United States)

    2016-11-15

    A new 2D Electron Cyclotron Emission Imaging (ECEI) diagnostic is being developed for the J-TEXT tokamak. It will provide the 2D electron temperature information with high spatial, temporal, and temperature resolution. The new ECEI instrument is being designed to support fundamental physics investigations on J-TEXT including MHD, disruption prediction, and energy transport. The diagnostic contains two dual dipole antenna arrays corresponding to F band (90-140 GHz) and W band (75-110 GHz), respectively, and comprises a total of 256 channels. The system can observe the same magnetic surface at both the high field side and low field side simultaneously. An advanced optical system has been designed which permits the two arrays to focus on a wide continuous region or two radially separate regions with high imaging spatial resolution. It also incorporates excellent field curvature correction with field curvature adjustment lenses. An overview of the diagnostic and the technical progress including the new remote control technique are presented.

  13. Electron cyclotron emission radiometer upgrade on the J-TEXT tokamak

    Energy Technology Data Exchange (ETDEWEB)

    Yang, Z. J.; Pan, X. M., E-mail: panxiaoming@hust.edu.cn; Ma, X. D.; Ruan, B. W.; Zhou, R. B.; Zhang, C. [State Key Laboratory of Advanced Electromagnetic Engineering and Technology, Huazhong University of Science and Technology, Wuhan, Hubei 430074 (China)

    2016-11-15

    To meet experimental requirements, the J-TEXT electron cyclotron emission (ECE) diagnostic is being upgraded. The front end antenna and transmission line have been modified and a new 8-channel W-band detecting unit has been developed. The improved ECE system will extend the frequency range from 94.5-124.5 GHz to 80.5-124.5 GHz. This will enable the system to cover the most plasma in the radius direction for B{sub T} = 1.8–2.2 T, and it even can cover almost the whole plasma range ρ = − 0.8–0.9 (minus means the high field side) at B{sub T} = 1.8 T. A new auxiliary channel bank with 8 narrow band, tunable yttrium iron garnet filters is planned to add to the ECE system. Due to observations along a major radius, perpendicular to B{sub T}, and relatively low electron temperature, Doppler and relativistic broadening are minimal and thus high spatial resolution measurements can be made at variable locations with these tunable channels.

  14. Assessing Greenhouse Gas emissions in the Greater Toronto Area using atmospheric observations (Invited)

    Science.gov (United States)

    Vogel, F. R.; Chan, E.; Huang, L.; Levin, I.; Worthy, D.

    2013-12-01

    Urban areas are said to be responsible for approximately 75% of anthropogenic Greenhouse Gases (GHGs) emissions while comprising only two percent of the land area [1]. This limited spatial expansion should facilitate a monitoring of anthropogenic GHGs from atmospheric observations. As major sources of emissions, cities also have a huge potential to drive emissions reductions. To effectively manage emissions, cities must however, first measure and report these publicly [2]. Modelling studies and measurements of CO2 from fossil fuel burning (FFCO2) in densely populated areas does, however, pose several challenges: Besides continuous in-situ observations, i.e. finding an adequate atmospheric transport model, a sufficiently fine-grained FFCO2 emission model and the proper background reference observations to distinguish the large-scale from the local/urban contributions to the observed FFCO2 concentration offsets ( ΔFFCO2) are required. Pilot studies which include the data from two 'sister sites*' in the vicinity of Toronto, Canada helped to derive flux estimates for Non-CO2 GHGs [3] and improve our understanding of urban FFCO2 emissions. Our 13CO2 observations reveal that the contribution of natural gas burning (mostly due to domestic heating) account for 80%×7% of FFCO2 emissions in the Greater Toronto Area (GTA) during winter. Our 14CO2 observations in the GTA, furthermore, show that the local offset of CO2 (ΔCO2) between our two sister sites can be largely attributed to urban FFCO2 emissions. The seasonal cycle of the observed ΔFFCO2 in Toronto, combined with high-resolution atmospheric modeling, helps to independently assess the contribution from different emission sectors (transportation, primary energy and industry, domestic heating) as predicted by a dedicated city-scale emission inventory, which deviates from a UNFCCC-based inventory. [1] D. Dodman. 2009. Blaming cities for climate change? An analysis of urban greenhouse gas emissions inventories

  15. Power electronics solution to dust emissions from thermal power plants

    Directory of Open Access Journals (Sweden)

    Vukosavić Slobodan

    2010-01-01

    Full Text Available Thermal power stations emit significant amounts of fly ash and ultra fine particles into the atmosphere. Electrostatic precipitators (ESP or electro filters remove flying ashes and fine particles from the flue gas before passing the gas into the chimney. Maximum allowable value of dust is 50 mg/m3 and it requires that the efficiency of the ESPs better than 99 %, which calls for an increase of active surface of the electrodes, hence increasing the filter volume and the weight of steel used for the filter. In previous decades, electrostatic precipitators in thermal power plants were fed by thyristor controlled, single phase fed devices having a high degree of reliability, but with a relatively low collection efficiency, hence requiring large effective surface of the collection plates and a large weight of steel construction in order to achieve the prescribed emission limits. Collection efficiency and energy efficiency of the electrostatic precipitator can be increased by applying high frequency high voltage power supply (HF HV. Electrical engineering faculty of the University of Belgrade (ETF has developed technology and HF HV equipment for the ESP power supply. This solution was subjected to extensive experimental investigation at TE Morava from 2008 to 2010. High frequency power supply is proven to reduce emission two times in controlled conditions while increasing energy efficiency of the precipitator, compared to the conventional thyristor controlled 50Hz supply. Two high frequency high voltage unit AR70/1000 with parameters 70 kV and 1000 mA are installed at TE Morava and thoroughly testes. It was found that the HF HV power supply of the ESP at TE Morava increases collection efficiency so that emission of fine particles and flying ashes are halved, brought down to only 50 % of the emissions encountered with conventional 50 Hz thyristor driven power supplies. On the basis of this study, conclusion is drawn that the equipment comprising HF HV

  16. Hard X-Ray Emission from Partially Occulted Solar Flares: RHESSI Observations in Two Solar Cycles

    Science.gov (United States)

    Effenberger, Frederic; Rubio da Costa, Fatima; Oka, Mitsuo; Saint-Hilaire, Pascal; Liu, Wei; Petrosian, Vahé; Glesener, Lindsay; Krucker, Säm

    2017-02-01

    Flares close to the solar limb, where the footpoints are occulted, can reveal the spectrum and structure of the coronal looptop source in X-rays. We aim at studying the properties of the corresponding energetic electrons near their acceleration site, without footpoint contamination. To this end, a statistical study of partially occulted flares observed with Reuven Ramaty High-Energy Solar Spectroscopic Imager is presented here, covering a large part of solar cycles 23 and 24. We perform detailed spectra, imaging, and light curve analyses for 116 flares and include contextual observations from SDO and STEREO when available, providing further insights into flare emission that were previously not accessible. We find that most spectra are fitted well with a thermal component plus a broken power-law, non-thermal component. A thin-target kappa distribution model gives satisfactory fits after the addition of a thermal component. X-ray imaging reveals small spatial separation between the thermal and non-thermal components, except for a few flares with a richer coronal source structure. A comprehensive light curve analysis shows a very good correlation between the derivative of the soft X-ray flux (from GOES) and the hard X-rays for a substantial number of flares, indicative of the Neupert effect. The results confirm that non-thermal particles are accelerated in the corona and estimated timescales support the validity of a thin-target scenario with similar magnitudes of thermal and non-thermal energy fluxes.

  17. FUSE Observations of QSOs behind Galaxy Clusters and of Galactic O VI Emission

    Science.gov (United States)

    Dixon, William V.

    2005-01-01

    We observed five quasars located behind clusters of galaxies with the goal of detecting resonant O VI absorption from warm (T approx. 10(exp 6) K) gas in the clusters' intracluster medium. The presence of such warm gas is predicted by cosmological hydrodynamic simulations and is observationally supported by the detection of "soft excess" emission in several galaxy clusters. A second goal was the detection of diffuse O VI emission from warm gas in our own Galaxy.

  18. Experimental Investigation of Charging Properties of Interstellar Type Silica Dust Grains by Secondary Electron Emissions

    Science.gov (United States)

    Tankosic, D.; Abbas, M. M.

    2013-01-01

    The dust charging by electron impact is an important dust charging processes in astrophysical and planetary environments. Incident low energy electrons are reflected or stick to the grains charging the dust grains negatively. At sufficiently high energies electrons penetrate the grains, leading to excitation and emission of electrons referred to as secondary electron emission (SEE). Available classical theoretical models for calculations of SEE yields are generally applicable for neutral, planar, or bulk surfaces. These models, however, are not valid for calculations of the electron impact charging properties of electrostatically charged micron/submicron-size dust grains in astrophysical environments. Rigorous quantum mechanical models are not yet available, and the SEE yields have to be determined experimentally for development of more accurate models for charging of individual dust grains. At the present time, very limited experimental data are available for charging of individual micron-size dust grains, particularly for low energy electron impact. The experimental results on individual, positively charged, micron-size lunar dust grains levitated carried out by us in a unique facility at NASA-MSFC, based on an electrodynamic balance, indicate that the SEE by electron impact is a complex process. The electron impact may lead to charging or discharging of dust grains depending upon the grain size, surface potential, electron energy, electron flux, grain composition, and configuration (Abbas et al, 2010, 2012). In this paper, we discuss SEE charging properties of individual micron-size silica microspheres that are believed to be analogs of a class of interstellar dust grains. The measurements indicate charging of the 0.2m silica particles when exposed to 25 eV electron beams and discharging when exposed to higher energy electron beams. Relatively large size silica particles (5.2-6.82m) generally discharge to lower equilibrium potentials at both electron energies

  19. Charging of Individual Micron-Size Interstellar/Planetary Dust Grains by Secondary Electron Emissions

    Science.gov (United States)

    Tankosic, D.; Abbas, M. M.

    2012-01-01

    Dust grains in various astrophysical environments are generally charged electrostatically by photoelectric emissions with UV/X-ray radiation, as well as by electron/ion impact. Knowledge of physical and optical properties of individual dust grains is required for understanding of the physical and dynamical processes in space environments and the role of dust in formation of stellar and planetary systems. In this paper, we discuss experimental results on dust charging by electron impact, where low energy electrons are scattered or stick to the dust grains, thereby charging the dust grains negatively, and at sufficiently high energies the incident electrons penetrate the grain leading to excitation and emission of electrons referred to as secondary electron emission (SEE). Currently, very limited experimental data are available for charging of individual micron-size dust grains, particularly by low energy electron impact. Available theoretical models based on the Sternglass equation (Sternglass, 1954) are applicable for neutral, planar, and bulk surfaces only. However, charging properties of individual micron-size dust grains are expected to be different from the values measured on bulk materials. Our recent experimental results on individual, positively charged, micron-size lunar dust grains levitated in an electrodynamic balance facility (at NASA-MSFC) indicate that the SEE by electron impact is a complex process. The electron impact may lead to charging or discharging of dust grains depending upon the grain size, surface potential, electron energy, electron flux, grain composition, and configuration (e.g. Abbas et al, 2010). Here we discuss the complex nature of SEE charging properties of individual micron-size lunar dust grains and silica microspheres.

  20. Modified electron acoustic field and energy applied to observation data

    Energy Technology Data Exchange (ETDEWEB)

    Abdelwahed, H. G., E-mail: hgomaa-eg@yahoo.com, E-mail: hgomaa-eg@mans.edu.eg [College of Science and Humanitarian Studies, Physics Department, Prince Sattam Bin Abdul Aziz University, Alkharj 11942 (Saudi Arabia); Theoretical Physics Research Group, Physics Department, Faculty of Science, Mansoura University, Mansoura 35516 (Egypt); El-Shewy, E. K. [Theoretical Physics Research Group, Physics Department, Faculty of Science, Mansoura University, Mansoura 35516 (Egypt)

    2016-08-15

    Improved electrostatic acoustic field and energy have been debated in vortex trapped hot electrons and fluid of cold electrons with pressure term plasmas. The perturbed higher-order modified-Korteweg-de Vries equation (PhomKdV) has been worked out. The effect of trapping and electron temperatures on the electro-field and energy properties in auroral plasmas has been inspected.

  1. Modeled and observed ozone sensitivity to mobile-source emissions in Mexico City

    Directory of Open Access Journals (Sweden)

    M. Zavala

    2009-01-01

    Full Text Available The emission characteristics of mobile sources in the Mexico City Metropolitan Area (MCMA have changed significantly over the past few decades in response to emission control policies, advancements in vehicle technologies and improvements in fuel quality, among others. Along with these changes, concurrent non-linear changes in photochemical levels and criteria pollutants have been observed, providing a unique opportunity to understand the effects of perturbations of mobile emission levels on the photochemistry in the region using observational and modeling approaches. The observed historical trends of ozone (O3, carbon monoxide (CO and nitrogen oxides (NOx suggest that ozone production in the MCMA has changed from a low to a high VOC-sensitive regime over a period of 20 years. Comparison of the historical emission trends of CO, NOx and hydrocarbons derived from mobile-source emission studies in the MCMA from 1991 to 2006 with the trends of the concentrations of CO, NOx, and the CO/NOx ratio during peak traffic hours also indicates that fuel-based fleet average emission factors have significantly decreased for CO and VOCs during this period whereas NOx emission factors do not show any strong trend, effectively reducing the ambient VOC/NOx ratio.

    This study presents the results of model analyses on the sensitivity of the observed ozone levels to the estimated historical changes in its precursors. The model sensitivity analyses used a well-validated base case simulation of a high pollution episode in the MCMA with the mathematical Decoupled Direct Method (DDM and the standard Brute Force Method (BFM in the 3-D CAMx chemical transport model. The model reproduces adequately the observed historical trends and current photochemical levels. Comparison of the BFM and the DDM sensitivity techniques indicates that the model yields ozone values that increase linearly with

  2. Immunolabeling for scanning electron microscopy (SEM) and field emission SEM.

    Science.gov (United States)

    Goldberg, Martin W

    2008-01-01

    Scanning electron microscopy (SEM) is a high resolution surface imaging technique. Many biological process and structures occur at surfaces and if antibodies are available, their components can be located within the surface structure. This is usually done in a similar way to immuno-fluorescence, using an unconjugated primary antibody followed by a tagged secondary antibody against the primary. In this case the tag is usually a colloidal gold particle instead of a fluorophore. Therefore it is quite straightforward to adapt an immuno-fluorescence procedure for SEM, as long as certain precautions are followed, as discussed here. Progressing from immuno-fluorescence, which essentially only indicates the position of a protein within the volume of a cell, to immuno-SEM, puts the labeling into the context of cellular structures. The principles and practices of sample preparation, labeling and imaging are described here.

  3. Chemical ionization mass spectrometry using carbon nanotube field emission electron sources.

    Science.gov (United States)

    Radauscher, Erich J; Keil, Adam D; Wells, Mitch; Amsden, Jason J; Piascik, Jeffrey R; Parker, Charles B; Stoner, Brian R; Glass, Jeffrey T

    2015-11-01

    A novel chemical ionization (CI) source has been developed based on a carbon nanotube (CNT) field emission electron source. The CNT-based electron source was evaluated and compared with a standard filament thermionic electron source in a commercial explosives trace detection desktop mass spectrometer. This work demonstrates the first reported use of a CNT-based ion source capable of collecting CI mass spectra. Both positive and negative modes were investigated. Spectra were collected for a standard mass spectrometer calibration compound, perfluorotributylamine (PFTBA), as well as trace explosives including trinitrotoluene (TNT), Research Department explosive (RDX), and pentaerythritol tetranitrate (PETN). The electrical characteristics, lifetime at operating pressure, and power requirements of the CNT-based electron source are reported. The CNT field emission electron sources demonstrated an average lifetime of 320 h when operated in constant emission mode under elevated CI pressures. The ability of the CNT field emission source to cycle on and off can provide enhanced lifetime and reduced power consumption without sacrificing performance and detection capabilities. Graphical Abstract ᅟ.

  4. Phenomenology of Neptune's radio emissions observed by the Voyager planetary radio astronomy experiment

    Science.gov (United States)

    Pedersen, B. M.; Lecacheux, A.; Zarka, P.; Aubier, M. G.; Kaiser, M. L.; Desch, M. D.

    1992-01-01

    The Neptune flyby in 1989 added a new planet to the known number of magnetized planets generating nonthermal radio emissions. We review the Neptunian radio emission morphology as observed by the planetary radio astronomy experiment on board Voyager 2 during a few weeks before and after closest approach. We present the characteristics of the two observed recurrent main components of the Neptunian kilometric radiation, i.e., the 'smooth' and the 'bursty' emissions, and we describe the many specific features of the radio spectrum during closest approach.

  5. Towards constraining megacity fossil-fuel emissions estimates with OCO-2 observations and Lagrangian modeling.

    Science.gov (United States)

    Kort, E. A.; Yang, E.; Ware, J.; Ye, X.; Lauvaux, T.; Wu, D.; Lin, J. C.; Oda, T.

    2016-12-01

    Rapid changes in human behavior are introducing significant perturbations to the Earth's carbon cycle and atmospheric balance of greenhouse gases. Emissions of carbon dioxide (CO2) are continuing to rise, and uncertainties in fossil-fuel emissions are increasing. Meanwhile urbanization continues to concentrate the global population in urban centers, and urban regions are now a dominant driver of global CO2 emissions. Observational constraints on fossil-fuel emissions and models representing fossil-fuel emissions are needed both to inform societal choices and to use atmospheric observations to study feedbacks in the natural carbon cycle. In this presentation we will discuss an approach we are developing that leverages space-based observations of total column carbon dioxide (XCO2, "top-down") and compares with simulated XCO2 values produced with a Lagrangian model coupled with different meteorological winds and multiple fossil-fuel inventories ("bottom-up"). We will highlight observational successes for measurements from the Orbiting Carbon Observatory 2 (OCO-2) and times when robust results are expected. We will further discuss questions that can be robustly answered with this framework and OCO-2 data and when techniques with greater fidelity are required, explaining limitations of the current observational-modeling system. Finally, we will discuss implications of these observational constraints on different bottom-up fossil-fuel emission estimates, and how such impliactions may impact interpretation of global OCO-2 data.

  6. Secondary electron emission from solid HD and a solid H2-D2 mixture

    DEFF Research Database (Denmark)

    Sørensen, H.; Børgesen, P.; Hao-Ming, Chen

    1983-01-01

    Secondary electron emission from solid HD and a solid 0.6 H2 + 0.4 D2 mixture has been studied for electron and hydrogen ion bombardment at primary energies from 0.5 to 3 keV and 2 to 10 keV/amu, respectively. The yield for solid HD is well explained by a simple stoichiometric model of the low......-energy stopping power for the internal secondaries. The secondary electron yield from the mixture is somewhat larger than the expected value, but lies between the values for pure solid H2 and D2. The secondary electron emission coefficient for solid tritium may be determined from a linear extrapolation...... of the present data....

  7. MM-wave emission by magnetized plasma during sub-relativistic electron beam relaxation

    Energy Technology Data Exchange (ETDEWEB)

    Ivanov, I. A., E-mail: Ivanov@inp.nsk.su; Arzhannikov, A. V.; Burmasov, V. S.; Popov, S. S.; Postupaev, V. V.; Sklyarov, V. F.; Vyacheslavov, L. N. [Budker Institute of Nuclear Physics, 11 Lavrentjev Avenue, Novosibirsk 630090 (Russian Federation); Novosibirsk State University, 2 Pirogova Street, Novosibirsk 630090 (Russian Federation); Burdakov, A. V.; Sorokina, N. V. [Budker Institute of Nuclear Physics, 11 Lavrentjev Avenue, Novosibirsk 630090 (Russian Federation); Novosibirsk State Technical University, 20 Karl Marx Avenue, Novosibirsk 630092 (Russian Federation); Gavrilenko, D. E.; Kasatov, A. A.; Kandaurov, I. V.; Mekler, K. I.; Rovenskikh, A. F.; Trunev, Yu. A. [Budker Institute of Nuclear Physics, 11 Lavrentjev Avenue, Novosibirsk 630090 (Russian Federation); Kurkuchekov, V. V.; Kuznetsov, S. A. [Novosibirsk State University, 2 Pirogova Street, Novosibirsk 630090 (Russian Federation); Polosatkin, S. V. [Budker Institute of Nuclear Physics, 11 Lavrentjev Avenue, Novosibirsk 630090 (Russian Federation); Novosibirsk State University, 2 Pirogova Street, Novosibirsk 630090 (Russian Federation); Novosibirsk State Technical University, 20 Karl Marx Avenue, Novosibirsk 630092 (Russian Federation)

    2015-12-15

    There are described electromagnetic spectra of radiation emitted by magnetized plasma during sub-relativistic electron beam in a double plasma frequency band. Experimental studies were performed at the multiple-mirror trap GOL-3. The electron beam had the following parameters: 70–110 keV for the electron energy, 1–10 MW for the beam power and 30–300 μs for its duration. The spectrum was measured in 75–230 GHz frequency band. The frequency of the emission follows variations in electron plasma density and magnetic field strength. The specific emission power on the length of the plasma column is estimated on the level 0.75 kW/cm.

  8. Coincident two-electron emission from surfaces by low-energy electrons

    Science.gov (United States)

    Gollisch, H.; Meinert, D.; Yi, Xiao; Feder, R.

    1997-04-01

    The simultaneous ejection of two electrons from non-magnetic surfaces due to the collision of incident low-energy electrons with valence electrons is treated in a relativistic distorted-wave Born approximation including exchange. The primary electron and the two emitted electrons are described by quasi-particle multiple scattering states. The valence electron is represented by linear combinations of Bloch waves matched at the surface. Screened Coulomb interaction matrix elements between these four states are evaluated. Numerical results for W(0 0 1) are presented and compared with one-dimensional bulk densities of states. Energy-integrated spectra and general features of the 2 e-distribution are in good agreement with recent experimental data.

  9. Observed decrease in atmospheric mercury explained by global decline in anthropogenic emissions

    Science.gov (United States)

    Yanxu Zhang,; Daniel J. Jacob,; Hannah M. Horowitz,; Long Chen,; Helen M. Amos,; Krabbenhoft, David P.; Franz Slemr,; Vincent L. St. Louis,; Elsie M. Sunderland,

    2015-01-01

    Observations of elemental mercury (Hg0) at sites in North America and Europe show large decreases (∼1–2% y−1) from 1990 to present. Observations in background northern hemisphere air, including Mauna Loa Observatory (Hawaii) and CARIBIC (Civil Aircraft for the Regular Investigation of the atmosphere Based on an Instrument Container) aircraft flights, show weaker decreases (inventories indicating flat or increasing emissions over that period. However, the inventories have three major flaws: (i) they do not account for the decline in atmospheric release of Hg from commercial products; (ii) they are biased in their estimate of artisanal and small-scale gold mining emissions; and (iii) they do not properly account for the change in Hg0/HgII speciation of emissions from coal-fired utilities after implementation of emission controls targeted at SO2 and NOx. We construct an improved global emission inventory for the period 1990 to 2010 accounting for the above factors and find a 20% decrease in total Hg emissions and a 30% decrease in anthropogenic Hg0 emissions, with much larger decreases in North America and Europe offsetting the effect of increasing emissions in Asia. Implementation of our inventory in a global 3D atmospheric Hg simulation [GEOS-Chem (Goddard Earth Observing System-Chemistry)] coupled to land and ocean reservoirs reproduces the observed large-scale trends in atmospheric Hg0 concentrations and in HgII wet deposition. The large trends observed in North America and Europe reflect the phase-out of Hg from commercial products as well as the cobenefit from SO2 and NOx emission controls on coal-fired utilities.

  10. Determining the spectra of radiation belt electron losses: Fitting DEMETER electron flux observations for typical and storm times

    OpenAIRE

    Whittaker, Ian C.; Gamble, Rory J.; Rodger, Craig J.; Clilverd, Mark A.; Sauvaud, Jean-André

    2013-01-01

    The energy spectra of energetic electron precipitation from the radiation belts are studied in order to improve our understanding of the influence of radiation belt processes. The Detection of Electromagnetic Emissions Transmitted from Earthquake Regions (DEMETER) microsatellite electron flux instrument is comparatively unusual in that it has very high energy resolution (128 channels with 17.9 keV widths in normal survey mode), which lends itself to this type of spectral analysis. Here electr...

  11. Artificial optical emissions at HAARP for pump frequencies near the third and second electron gyro-harmonic

    Directory of Open Access Journals (Sweden)

    M. J. Kosch

    2005-07-01

    Full Text Available High-power high-frequency radio waves beamed into the ionosphere cause plasma turbulence, which can accelerate electrons. These electrons collide with the F-layer neutral oxygen causing artificial optical emissions identical to natural aurora. Pumping at electron gyro-harmonic frequencies has special significance as many phenomena change their character. In particular, artificial optical emissions become strongly reduced for the third and higher gyro-harmonics. The High frequency Active Auroral Research Program (HAARP facility is unique in that it can select a frequency near the second gyro-harmonic. On 25 February 2004, HAARP was operated near the third and passed through the second gyro-harmonic for the first time in a weakening ionosphere. Two novel observations are: firstly, a strong enhancement of the artificial optical emission intensity near the second gyro-harmonic, which is opposite to higher gyro-harmonics; secondly, the optical enhancement maximum occurs for frequencies just above the second gyro-harmonic. We provide the first experimental evidence for these effects, which have been predicted theoretically. In addition, irregular optical structures were created when the pump frequency was above the ionospheric critical frequency.

    Keywords. Active experiments – Auroral ionosphere – Wave-particle interactions

  12. Electron beam technology for multipollutant emissions control from heavy fuel oil-fired boiler.

    Science.gov (United States)

    Chmielewski, Andrzej G; Ostapczuk, Anna; Licki, Janusz

    2010-08-01

    The electron beam treatment technology for purification of exhaust gases from the burning of heavy fuel oil (HFO) mazout with sulfur content approximately 3 wt % was tested at the Institute of Nuclear Chemistry and Technology laboratory plant. The parametric study was conducted to determine the sulfur dioxide (SO2), oxides of nitrogen (NO(x)), and polycyclic aromatic hydrocarbon (PAH) removal efficiency as a function of temperature and humidity of irradiated gases, absorbed irradiation dose, and ammonia stoichiometry process parameters. In the test performed under optimal conditions with an irradiation dose of 12.4 kGy, simultaneous removal efficiencies of approximately 98% for SO2, and 80% for NO(x) were recorded. The simultaneous decrease of PAH and one-ringed aromatic hydrocarbon (benzene, toluene, and xylenes [BTX]) concentrations was observed in the irradiated flue gas. Overall removal efficiencies of approximately 42% for PAHs and 86% for BTXs were achieved with an irradiation dose 5.3 kGy. The decomposition ratio of these compounds increased with an increase of absorbed dose. The decrease of PAH and BTX concentrations was followed by the increase of oxygen-containing aromatic hydrocarbon concentrations. The PAH and BTX decomposition process was initialized through the reaction with hydroxyl radicals that formed in the electron beam irradiated flue gas. Their decomposition process is based on similar principles as the primary reaction concerning SO2 and NO(x) removal; that is, free radicals attack organic compound chains or rings, causing volatile organic compound decomposition. Thus, the electron beam flue gas treatment (EBFGT) technology ensures simultaneous removal of acid (SO2 and NO(x)) and organic (PAH and BTX) pollutants from flue gas emitted from burning of HFO. This technology is a multipollutant emission control technology that can be applied for treatment of flue gas emitted from coal-, lignite-, and HFO-fired boilers. Other thermal processes such

  13. Influence of the charge changing processes on proton induced electron emission from polycrystalline aluminium

    CERN Document Server

    Pauly, N; Rösler, M

    2003-01-01

    Charge changing processes are known to have a strong influence on ion-induced electron emission characteristics. However, up to now, only a few theoretical models incorporate electron capture and loss cross-sections. For protons with velocities around 1 a.u., a correct theoretical model of the various charge changing processes undergone by the proton is necessary. In particular, all the electrons excited in the different processes have to be taken into account. It is precisely the aim of the present paper to give a description of all the possible charge changing processes and to incorporate these processes in a Monte Carlo simulation of proton induced electron emission from polycrystalline aluminium. The influence of charge changing processes on backward electron emission yield is evaluated. The contributions of H sup + , H sup 0 , H sup - fractions as well as of electrons excited by the charge changing processes for incident H sup + (1

  14. HST-COS Observations on Hydrogen, Helium, Carbon, and Nitrogen Emission from the SN 1987A Reverse Shock

    Science.gov (United States)

    France, Kevin; McCray, Richard; Penton, Steven V.; Kirshner, Robert P.; Challis, Peter; Laming, J. Martin; Bouchet, Patrice; Chevalier, Roger; Garnavich, Peter M.; Fransson, Claes; hide

    2011-01-01

    We present the most sensitive ultraviolet observations of Supernova 1987 A to date. Imaging spectroscopy from the Hubble Space Telescope-Cosmic Origins Spectrograph shows many narrow (Delta v approximates 300 km/s) emission lines from the circumstellar ring, broad Delta v approximates 10-20 x 10(exp 3) km/s) emission lines from the reverse shock, and ultraviolet continuum emission. The high signal-to-noise ratio (>40 per resolution element) broad Ly-alpha emission is excited by soft X-ray and EUV heating of mostly neutral gas in the circumstellar ring and outer supernova debris. The ultraviolet continuum at lambda > 1350 A can be explained by H-I two-photon (2s(exp 2)S(sub 1/2)-l(exp 2)S(sub 1/2)) emission from the same region. We confirm our earlier, tentative detection of N V lambda 1240 emission from the reverse shock and present the first detections of broad He II lambda1640, C IV lambda 1550, and N IV ] lambda1486 emission lines from the reverse shock. The helium abundance in the high-velocity material is He/H = 0.14 +/- 0.06. The N V /H alpha line ratio requires partial ion-electron equilibration (T(sub e)/T(sub p) approximately equal to 0.14-0.35). We find that the N/C abundance ratio in the gas crossing the reverse shock is significantly higher than that in the circumstellar ring, a result that may be attributed to chemical stratification in the outer envelope of the supernova progenitor. The N/C abundance may have been stratified prior to the ring expUlsion, or this result may indicate continued CNO processing in the progenitor subsequent to the expUlsion of the circumstellar ring.

  15. Satellite observations of atmospheric methane and their value for quantifying methane emissions

    Directory of Open Access Journals (Sweden)

    D. J. Jacob

    2016-11-01

    Full Text Available Methane is a greenhouse gas emitted by a range of natural and anthropogenic sources. Atmospheric methane has been measured continuously from space since 2003, and new instruments are planned for launch in the near future that will greatly expand the capabilities of space-based observations. We review the value of current, future, and proposed satellite observations to better quantify and understand methane emissions through inverse analyses, from the global scale down to the scale of point sources and in combination with suborbital (surface and aircraft data. Current global observations from Greenhouse Gases Observing Satellite (GOSAT are of high quality but have sparse spatial coverage. They can quantify methane emissions on a regional scale (100–1000 km through multiyear averaging. The Tropospheric Monitoring Instrument (TROPOMI, to be launched in 2017, is expected to quantify daily emissions on the regional scale and will also effectively detect large point sources. A different observing strategy by GHGSat (launched in June 2016 is to target limited viewing domains with very fine pixel resolution in order to detect a wide range of methane point sources. Geostationary observation of methane, still in the proposal stage, will have the unique capability of mapping source regions with high resolution, detecting transient "super-emitter" point sources and resolving diurnal variation of emissions from sources such as wetlands and manure. Exploiting these rapidly expanding satellite measurement capabilities to quantify methane emissions requires a parallel effort to construct high-quality spatially and sectorally resolved emission inventories. Partnership between top-down inverse analyses of atmospheric data and bottom-up construction of emission inventories is crucial to better understanding methane emission processes and subsequently informing climate policy.

  16. Two-dimensional simulation research of secondary electron emission avalanche discharge on vacuum insulator surface

    Science.gov (United States)

    Cai, Libing; Wang, Jianguo; Zhu, Xiangqin; Wang, Yue; Zhang, Dianhui

    2015-01-01

    Based on the secondary electron emission avalanche (SEEA) model, the SEEA discharge on the vacuum insulator surface is simulated by using a 2D PIC-MCC code developed by ourselves. The evolutions of the number of discharge electrons, insulator surface charge, current, and 2D particle distribution are obtained. The effects of the strength of the applied electric field, secondary electron yield coefficient, rise time of the pulse, length of the insulator on the discharge are investigated. The results show that the number of the SEEA electrons presents a quadratic dependence upon the applied field strength. The SEEA current, which is on the order of Ampere, is directly proportional to the field strength and secondary electron yield coefficient. Finally, the electron-stimulated outgassing is included in the simulation code, and a three-phase discharge curve is presented by the simulation, which agrees with the experimental data.

  17. Developing field emission electron sources based on ultrananocrystalline diamond for accelerators

    Energy Technology Data Exchange (ETDEWEB)

    Baryshev, Sergey V.; Jing, Chunguang; Qiu, Jiaqi; Antipov, Sergey; Jabotinski, Vadim; Shao, Jiahang; Gai, Wei; Sumant, Anirudha V.

    2016-08-25

    Radiofrequency (RF) electron guns work by establishing an RF electromagnetic field inside a cavity having conducting walls. Electrons from a cathode are generated in the injector and immediately become accelerated by the RF electric field, and exit the gun as a series of electron bunches. Finding simple solutions for electron injection is a long standing problem. While energies of 30-50 MeV are achievable in linear accelerators (linacs), finding an electron source able to survive under MW electric loads and provide an average current of 1-10 mA is important. Meeting these requirements would open various linac applications for industry. The natural way to simplify and integrate RF injector architectures with the electron source would be to place the source directly into the RF cavity with no need for additional heaters/lasers. Euclid TechLabs in collaboration with Argonne National Lab are prototyping a family of highly effective field emission electron sources based on a nitrogen-incorporated ultrananocrystalline diamond ((N)UNCD) platform. Determined metrics suggest that our emitters are emissive enough to meet requirements for magnetized cooling at electron-ion colliders, linac-based radioisotope production and X-ray sterilization, and others.

  18. Electron Emission Properties of Insulator Materials Pertinent to the International Space Station

    Science.gov (United States)

    Thomson, C. D.; Zavyalov, V.; Dennison, J. R.; Corbridge, Jodie

    2004-01-01

    We present the results of our measurements of the electron emission properties of selected insulating and conducting materials used on the International Space Station (ISS). Utah State University (USU) has performed measurements of the electron-, ion-, and photon-induced electron emission properties of conductors for a few years, and has recently extended our capabilities to measure electron yields of insulators, allowing us to significantly expand current spacecraft material charging databases. These ISS materials data are used here to illustrate our various insulator measurement techniques that include: i) Studies of electron-induced secondary and backscattered electron yield curves using pulsed, low current electron beams to minimize deleterious affects of insulator charging. ii) Comparison of several methods used to determine the insulator 1st and 2nd crossover energies. These incident electron energies induce unity total yield at the transition between yields greater than and less than one with either negative or positive charging, respectively. The crossover energies are very important in determining both the polarity and magnitude of spacecraft surface potentials. iii) Evolution of electron emission energy spectra as a function of insulator charging used to determine the surface potential of insulators. iv) Surface potential evolution as a function of pulsed-electron fluence to determine how quickly insulators charge, and how this can affect subsequent electron yields. v) Critical incident electron energies resulting in electrical breakdown of insulator materials and the effect of breakdown on subsequent emission, charging and conduction. vi) Charge-neutralization techniques such as low-energy electron flooding and UV light irradiation to dissipate both positive and negative surface potentials during yield measurements. Specific ISS materials being tested at USU include chromic and sulfuric anodized aluminum, RTV-silicone solar array adhesives, solar cell

  19. Ion milling coupled field emission scanning electron microscopy reveals current misunderstanding of morphology of polymeric nanoparticles.

    Science.gov (United States)

    Francis, Donny; Mouftah, Samiha; Steffen, Robert; Beduneau, Arnaud; Pellequer, Yann; Lamprecht, Alf

    2015-01-01

    Nanoparticles (NPs) are currently used as drug delivery systems for numerous therapeutic macromolecules, e.g. proteins or DNA. Based on the preparation by double emulsion solvent evaporation a sponge-like structure was postulated entrapping hydrophilic drugs inside an internal aqueous phase. However, a direct proof of this hypothesized structure is still missing today. NPs were prepared from different polymers using a double-emulsion method and characterized for their physicochemical properties. Combining ion milling with field emission scanning electron microscopy allowed to cross section single NP and to visualize their internal morphology. The imaging procedure permitted cross-sectioning of NPs and visualization of the internal structure as well as localizing drugs associated with NPs. It was observed that none of the model actives was encapsulated inside the polymeric matrix when particle diameters were below around 470 nm but predominantly adsorbed to the particle surface. Even at larger diameters only a minority of particles of a diameter below 1 μm contained an internal phase. The properties of such drug loaded NPs, i.e. drug release or the observations in cellular uptake or even drug targeting needs to be interpreted carefully since in most cases NP surface properties are potentially dominated by the 'encapsulated' drug characteristics. Copyright © 2014 Elsevier B.V. All rights reserved.

  20. Indirect Immunodetection of Fungal Fragments by Field Emission Scanning Electron Microscopy.

    Science.gov (United States)

    Afanou, Komlavi Anani; Straumfors, Anne; Skogstad, Asbjørn; Nayak, Ajay P; Skaar, Ida; Hjeljord, Linda; Tronsmo, Arne; Eduard, Wijnand; Green, Brett James

    2015-09-01

    Submicronic fungal fragments have been observed in in vitro aerosolization experiments. The occurrence of these particles has therefore been suggested to contribute to respiratory health problems observed in mold-contaminated indoor environments. However, the role of submicronic fragments in exacerbating adverse health effects has remained unclear due to limitations associated with detection methods. In the present study, we report the development of an indirect immunodetection assay that utilizes chicken polyclonal antibodies developed against spores from Aspergillus versicolor and high-resolution field emission scanning electron microscopy (FESEM). Immunolabeling was performed with A. versicolor fragments immobilized and fixed onto poly-l-lysine-coated polycarbonate filters. Ninety percent of submicronic fragments and 1- to 2-μm fragments, compared to 100% of >2-μm fragments generated from pure freeze-dried mycelial fragments of A. versicolor, were positively labeled. In proof-of-concept experiments, air samples collected from moldy indoor environments were evaluated using the immunolabeling technique. Our results indicated that 13% of the total collected particles were derived from fungi. This fraction comprises 79% of the fragments that were detected by immunolabeling and 21% of the spore particles that were morphologically identified. The methods reported in this study enable the enumeration of fungal particles, including submicronic fragments, in a complex heterogeneous environmental sample. Copyright © 2015, American Society for Microbiology. All Rights Reserved.

  1. Observation of the sweating in lipstick by scanning electron microscopy.

    Science.gov (United States)

    Seo, S Y; Lee, I S; Shin, H Y; Choi, K Y; Kang, S H; Ahn, H J

    1999-06-01

    The relationship between the wax matrix in lipstick and sweating has been investigated by observing the change of size and shape of the wax matrix due to sweating by Scanning Electron Microscopy (SEM). For observation by SEM, a lipstick sample was frozen in liquid nitrogen. The oil in the lipstick was then extracted in cold isopropanol (-70 degrees C) for 1-3 days. After the isopropanol was evaporated, the sample was sputtered with gold and examined by SEM. The change of wax matrix underneath the surface from fine, uniform structure to coarse, nonuniform structure resulted from the caking of surrounding wax matrix. The oil underneath the surface migrated to the surface of lipstick with sweating; consequently the wax matrix in that region was rearranged into the coarse matrix. In case of flamed lipstick, sweating was delayed and the wax matrix was much coarser than that of the unflamed one. The larger wax matrix at the surface region was good for including oil. The effect of molding temperature on sweating was also studied. As the molding temperature rose, sweating was greatly reduced and the size of the wax matrix increased. It was found that sweating was influenced by the compatibility of wax and oil. A formula consisting of wax and oil that have good compatibility has a tendency to reduce sweating and increase the size of the wax matrix. When pigments were added to wax and oil, the size of the wax matrix was changed, but in all cases sweating was increased due to the weakening of the binding force between wax and oil. On observing the thick membrane of wax at the surface of lipstick a month after molding it was also found that sweating was influenced by ageing. In conclusion, the structure of the wax matrix at the surface region of lipstick was changed with the process of flaming, molding temperature, compatibility of wax and oil, addition of pigment, and ageing. In most cases, as the size of the wax matrix was increased, sweating was reduced and delayed.

  2. Field Emission Vacuum (FEV) Electronic Devices for Operation Above 500 Degrees Celsius

    Science.gov (United States)

    Peltz, L.; Jones, W. M.; Frampton, R. V.; Keith, A. R.; Scherer, A.

    2017-11-01

    Boeing is teamed with Caltech to develop FEV (Field-Emission Vacuum) electronics. Our Boeing-Caltech team has recently begun work, under NASA ROSES C.24 HOTTech program, to demonstrate robust FEV operating at 500C, towards Venus surface missions.

  3. Enhanced electron field emission from carbon nanotubes irradiated by energetic C ions.

    Science.gov (United States)

    Sun, Peng-Cheng; Deng, Jian-Hua; Cheng, Guo-An; Zheng, Rui-Ting; Ping, Zhao-Xia

    2012-08-01

    The field emission performance and structure of the vertically aligned multi-walled carbon nanotube arrays irradiated by energetic C ion with average energy of 40 keV have been investigated. During energetic C ion irradiation, the curves of emission current density versus the applied field of samples shift firstly to low applied fields when the irradiation doses are less than 9.6 x 10(16) cm(-2), and further increase of dose makes the curves reversing to a high applied field, which shows that high dose irradiation in carbon nanotube arrays makes their field emission performance worse. After energetic ion irradiation with a dose of 9.6 x 1016 cm(-2), the turn-on electric field and the threshold electric field of samples decreased from 0.80 and 1.13 V/microm to 0.67 and 0.98 V/microm respectively. Structural analysis of scanning electron microscopy, transmission electron microscopy and Raman spectroscopy indicates that the amorphous carbon nanowire/carbon nanotube hetero nano-structures have been fabricated in the C ion irradiated carbon nanotubes. The enhancement of electron field emission is due to the formation of amorphous carbon nanowires at the tip of carbon nanotube arrays, which is an electron emitting material with low work function.

  4. Electron emission yields from boron-like Ar ions impinging on Au(100)

    NARCIS (Netherlands)

    Bodewits, E.; Bekker, H.; de Nijs, A. J.; Hoekstra, R.; Winklehner, D.; Daniel, B.; Kowarik, G.; Dobes, K.; Aumayr, F.

    2011-01-01

    Using a new experimental station to be installed at the HITRAP facility at GSI we studied electron emission yields of Ar13+ ions impinging on a clean Au(1 00) surface. By taking data under different incidence angles and at different initial kinetic energies, contributions from kinetic and potential

  5. Field electron emission from hydrogen plasma treated nano-ZnO thin films.

    Science.gov (United States)

    Wang, Xiao-Ping; Liu, Xin-Xin; Wang, Li-Jun; Li, Huai-Hui; Mei, Cui-Yu; Liu, Xiao-Fei; Can, Yang

    2012-08-01

    A nano-Zno films are deposited on the Mo film/ceramic substrates by using the electron beam vapor deposition technique. Then a hydrogen plasma treated method is used to improve the characteristics of ZnO thin films by microwave plasma chemical vapor deposition system. Effects of process parameters on morphologies and structures of the ZnO thin films are detected and analysed by field emission scanning electron microscopy, X-ray diffraction spectrum and energy dispersive spectrum. The experimental result indicates that the hydrogen plasma treated techniques can essentially reduce the surface resistance and improve the field emission current density of the nano-ZnO thin films. For the hydrogen plasma treated sample, its field emission current density can increased more than three times at 2.2 V/microm electric field condition.

  6. Higher harmonic emission by a relativistic electron beam in a longitudinal magnetic wiggler

    Science.gov (United States)

    Davidson, Ronald C.; McMullin, Wayne A.

    1982-10-01

    The classical limit of the Einstein-coefficient method is used in the low-gain regime to calculate the stimulated emission from a tenuous relativistic electron beam propagating in the combined solenoidal and longitudinal wiggler fields (B0+δB k0z)e^z produced near the axis of a multiple-mirror (undulator) field configuration. Emission is found to occur at all harmonics of the wiggler wave number k0 with Doppler upshifted output frequency given by ω=(lk0Vb+ωcb)(1+Vbc)γ2b(1+γ2bV2⊥c2), where l>=1. The emission is compared to the low-gain cyclotron maser with δB=0 and to the low-gain free-electron laser (operating at higher harmonics) utilizing a transverse linearly polarized wiggler field.

  7. Proposal to detect an emission of unusual super-high energy electrons in electron storage rings

    Directory of Open Access Journals (Sweden)

    Da-peng Qian

    2014-01-01

    Full Text Available According to an extended Lorentz–Einstein mass formula taken into the uncertainty principle, it is predicted that the electron beams passing accelerating electric field should with a small probability generate abnormal super-high energy electrons which are much higher than the beam energy. Author’s preliminary experiment result at electron storage ring has hinted these signs, so suggests to more strictly detect this unusual phenomenon, and thus to test the extended mass formula as well as a more perfect special relativity.

  8. Suppression of electron emission from metal electrodes : LDRD 28771 final report.

    Energy Technology Data Exchange (ETDEWEB)

    Stygar, William A.; Savage, Mark Edward; Ives, Harry Crockett, III; Johnson, David J.; Fowler, William E.

    2003-11-01

    This research consisted of testing surface treatment processes for stainless steel and aluminum for the purpose of suppressing electron emission over large surface areas to improve the pulsed high voltage hold-off capabilities of these metals. Improvements to hold-off would be beneficial to the operation of the vacuum-insulator grading rings and final self-magnetically insulated transmission line on the ZR-upgrade machine and other pulsed power applications such as flash radiograph and pulsed-microwave machines. The treatments tested for stainless steel include the Z-protocol (chemical polish, HVFF, and gold coating), pulsed E-beam surface treatments by IHCE, Russia, and chromium oxide coatings. Treatments for aluminum were anodized and polymer coatings. Breakdown thresholds also were measured for a range of surface finishes and gap distances. The study found that: (1.) Electrical conditioning and solvent cleaning in a filtered air environment each improve HV hold-off 30%. (2.) Anodized coatings on aluminum give a factor of two improvement in high voltage hold-off. However, anodized aluminum loses this improvement when the damage is severe. Chromium oxide coatings on stainless steel give a 40% and 20% improvement in hold-off before and after damage from many arcs. (3.) Bare aluminum gives similar hold-off for surface roughness, R{sub a}, ranging from 0.08 to 3.2 {micro}m. (4.) The various EBEST surfaces tested give high voltage hold-off a factor of two better than typical machined and similar to R{sub a} = 0.05 {micro}m polished stainless steel surfaces. (5.) For gaps > 2 mm the hold-off voltage increases as the square root of the gap for bare metal surfaces. This is inconsistent with the accepted model for metals that involves E-field induced electron emission from dielectric inclusions. Micro-particles accelerated across the gap during the voltage pulse give the observed voltage dependence. However the similarity in observed breakdown times for large and small

  9. Enhanced performance of thermal-assisted electron field emission based on barium oxide nanowire

    Energy Technology Data Exchange (ETDEWEB)

    Cui, Yunkang [Department of Mathematics and Physics, Nanjing Institute of technology, Nanjing, 211167 (China); Chen, Jing, E-mail: chenjingmoon@gmail.com [School of Electronic Science & Engineering, Southeast University, Nanjing, 210096 (China); Zhang, Yuning; Zhang, Xiaobing; Lei, Wei; Di, Yunsong [School of Electronic Science & Engineering, Southeast University, Nanjing, 210096 (China); Zhang, Zichen, E-mail: zz241@ime.ac.cn [Integrated system for Laser applications Group, Institute of Microelectronics of Chinese Academy of Sciences, 100029, Beijing (China)

    2017-02-28

    Highlights: • A possible mechanism for thermal-assisted electric field was demonstrated. • A new path for the architecture of the novel nanomaterial and methodology for its potential application in the field emission device area was provided. • The turn-on field, the threshold field and the field emission current density were largely related to the temperature of the cathode. • The relationship between the work function of emitter material and the temperature of emitter was found. - Abstract: In this paper, thermal-assisted field emission properties of barium oxide (BaO) nanowire synthesized by a chemical bath deposition method were investigated. The morphology and composition of BaO nanowire were characterized by field emission scanning electron microscopy (FESEM), high resolution transmission electron microscopy (HRTEM), selected area electron diffraction (SED), X-ray diffraction (XRD), and energy dispersive X-ray spectrometer (EDX) respectively. The turn-on field, threshold field and the emission current density could be affected relatively due to the thermal-assisted effect when the electric field was applied, in the meanwhile, the turn-on field for BaO nanowire was measured to be decreased from 1.12 V/μm to 0.66 V/μm when the temperature was raised from 293 K to 593 K, whereas for the threshold field was found to decrease from 3.64 V/μm to 2.12 V/μm. The improved performance was demonstrated due to the reduced work function of the BaO nanowire as the agitation temperature increasing, leading to the higher probability of electrons tunneling through the energy barrier and enhancement of the field emission properties of BaO emitters.

  10. HIGH-CURRENT COLD CATHODE FIELD EMISSION ARRAY FOR ELECTRON LENS APPLICATION

    Energy Technology Data Exchange (ETDEWEB)

    Hirshfield, Jay L

    2012-12-28

    During Phase I, the following goals were achieved: (1) design and fabrication of a novel, nano-dimensional CNT field emitter assembly for high current density application, with high durability; (2) fabrication of a ceramic based micro channel plate (MCP) and characterization of its secondary electron emission; and (3) characterizing the CNT/MCP cathode for high field emission and durability. As a result of these achievements, a relatively high current density of ~ 1.2 A/cm2 from a CNT cathode and single channel MCP were measured. The emission current was also extremely stable with a peak-to-peak variation of only 1.8%. The emission current could be further enhanced to meet requirements for electron lens applications by increasing the number of MCP channels. A calculation for maximum possible current density with a 1200 channel/cm2 MCP, placed over a cathode with 1200 uniformly functioning CNTs, would be ~1.46 kA/cm2, neglecting space charge limitations. Clearly this level of emission is far greater than what is needed for the electron lens application, but it does offer a highly comforting margin to account for sub-standard emitters and/or to allow the lesser challenge of building a cathode with fewer channels/cm2. A satisfactory goal for the electron lens application would be a controllable emission of 2-4 mA per channel in an ensemble of 800-1200 uniformly-functioning channels/cm2, and a cathode with overall area of about 1 cm2.

  11. High-current electron gun with a planar magnetron integrated with an explosive-emission cathode

    Science.gov (United States)

    Kiziridi, P. P.; Ozur, G. E.

    2017-05-01

    A new high-current electron gun with plasma anode and explosive-emission cathode integrated with planar pulsed powered magnetron is described. Five hundred twelve copper wires 1 mm in diameter and 15 mm in height serve as emitters. These emitters are installed on stainless steel disc (substrate) with 3-mm distance between them. Magnetron discharge plasma provides increased ion density on the periphery of plasma anode formed by high-current Penning discharge ignited within several milliseconds after starting of the magnetron discharge. The increased on the periphery ion density improves the uniformity of high-current electron beam produced in such an electron gun.

  12. Bistable Intrinsic Charge Fluctuations of a Dust Grain Subject to Secondary Electron Emission in a Plasma

    CERN Document Server

    Shotorban, Babak

    2015-01-01

    A master equation was formulated to study intrinsic charge fluctuations of a grain in a plasma as ions and primary electrons are attached to the grain through collisional collection, and secondary electrons are emitted from the grain. Two different plasmas with Maxwellian and non-Maxwellian distributions were considered. The fluctuations could be bistable in either plasma when the secondary electron emission is present, as two stable macrostates, associated with two stable roots of the charge net current, may exist. Metastablity of fluctuations, manifested by the passage of the grain charge between two macrostates, was shown to be possible.

  13. Atmospheric observations show accurate reporting and little growth in India's methane emissions.

    Science.gov (United States)

    Ganesan, Anita L; Rigby, Matt; Lunt, Mark F; Parker, Robert J; Boesch, Hartmut; Goulding, N; Umezawa, Taku; Zahn, Andreas; Chatterjee, Abhijit; Prinn, Ronald G; Tiwari, Yogesh K; van der Schoot, Marcel; Krummel, Paul B

    2017-10-10

    Changes in tropical wetland, ruminant or rice emissions are thought to have played a role in recent variations in atmospheric methane (CH4) concentrations. India has the world's largest ruminant population and produces ~ 20% of the world's rice. Therefore, changes in these sources could have significant implications for global warming. Here, we infer India's CH4 emissions for the period 2010-2015 using a combination of satellite, surface and aircraft data. We apply a high-resolution atmospheric transport model to simulate data from these platforms to infer fluxes at sub-national scales and to quantify changes in rice emissions. We find that average emissions over this period are 22.0 (19.6-24.3) Tg yr(-1), which is consistent with the emissions reported by India to the United Framework Convention on Climate Change. Annual emissions have not changed significantly (0.2 ± 0.7 Tg yr(-1)) between 2010 and 2015, suggesting that major CH4 sources did not change appreciably. These findings are in contrast to another major economy, China, which has shown significant growth in recent years due to increasing fossil fuel emissions. However, the trend in a global emission inventory has been overestimated for China due to incorrect rate of fossil fuel growth. Here, we find growth has been overestimated in India but likely due to ruminant and waste sectors.India's methane emissions have been quantified using atmospheric measurements to provide an independent comparison with reported emissions. Here Ganesan et al. find that derived methane emissions are consistent with India's reports and no significant trend has been observed between 2010-2015.

  14. Panchromatic Observations of the Textbook GRB 110205A: Constraining Physical Mechanisms of Prompt Emission and Afterglow

    Science.gov (United States)

    Zheng, W.; Shen, R. F.; Sakamoto, T.; Beardmore, A. P.; De Pasquale, M.; Wu, X. F.; Gorosabel, J.; Urata, Y.; Sugita, S.; Zhang, B.; hide

    2011-01-01

    We present a comprehensive analysis of a bright, long duration (T(sub 90) approx. 257 s) GRB 110205A at redshift z = 2.22. The optical prompt emission was detected by Swift/UVOT, ROTSE-IIIb and BOOTES telescopes when the GRB was still radiating in the gamma-ray band. Thanks to its long duration, nearly 200 s of observations were obtained simultaneously from optical, X-ray to gamma-ray (1 eV - 5 MeV), which makes it one of the exceptional cases to study the broadband spectral energy distribution across 6 orders of magnitude in energy during the prompt emission phase. In particular, by fitting the time resolved prompt spectra, we clearly identify, for the first time, an interesting two-break energy spectrum, roughly consistent with the standard GRB synchrotron emission model in the fast cooling regime. Although the prompt optical emission is brighter than the extrapolation of the best fit X/ -ray spectra, it traces the -ray light curve shape, suggesting a relation to the prompt high energy emission. The synchrotron + synchrotron self-Compton (SSC) scenario is disfavored by the data, but the models invoking a pair of internal shocks or having two emission regions can interpret the data well. Shortly after prompt emission (approx. 1100 s), a bright (R = 14.0) optical emission hump with very steep rise ( alpha approx. 5.5) was observed which we interpret as the emission from the reverse shock. It is the first time that the rising phase of a reverse shock component has been closely observed.

  15. Kalman Filter Inversion of Regional NOx Emissions based on OMI NO2 Observations

    Science.gov (United States)

    Cohan, D. S.; Tang, W.

    2012-12-01

    Nitrogen oxides (NOx) are crucial precursors of tropospheric ozone and particulate matter. Uncertain emissions inventories for NOx are among the leading causes of uncertainty in photochemical models used to inform air quality management. Emission inventories derived from bottom-up approaches typically serve as the basis for state implementation plans and other regulatory modeling. However, inverse modeling can be used to create top-down estimates of emissions based on observed pollutant levels in order to evaluate or supplement traditional inventories. Here, we apply NO2 column densities observed by the OMI instrument aboard the Aura satellite (OMI Standard Product version 2.0) to estimate top-down NOx emission rates for seven urban and rural regions of east Texas. The CAMx photochemical model with Decoupled Direct Method (DDM) sensitivity analysis is applied to simulate 3-dimensional fields of NO2 concentrations and their sensitivities to NOx emissions from each region, starting from an emissions inventory used in recent Texas ozone attainment planning. Averaging kernels from the OMI retrievals are used to adjust CAMx results to corresponding column densities. Lightning NO emissions are added to the a priori inventory based on National Lightning Detection Network data, which rectifies a portion of the underprediction of NO2 in rural regions. A Kalman Filter inversion is applied to estimate regional emissions scaling factors that yield best agreement between CAMx and OMI results, using an iterative approach until convergence is achieved. Pseudo-data testing demonstrates that the Kalman Filter can rectify known perturbations to a base field within four iterations. Ambient observations of NOx from regulatory monitors and from the Texas Air Quality Study 2006 field campaign are used to evaluate the original and top-down emissions inventories. Both inventories are applied in the CAMx simulations of Texas ozone attainment modeling episodes to evaluate differences in

  16. Simulations of electromagnetic emissions produced in a thin plasma by a continuously injected electron beam

    CERN Document Server

    Annenkov, V V; Volchok, E P

    2015-01-01

    In this paper, electromagnetic emissions produced in a thin beam-plasma system are studied using two-dimensional particle-in-cell simulations. For the first time, the problem of emission generation in such a system is considered in the realistic formulation allowing for the continuous injection of a relativistic electron beam through the plasma boundary. Specific attention is given to the thin plasma case in which the transverse plasma size is comparable to the typical wavelength of beam-driven oscillations. Such a case is often implemented in laboratory beam-plasma experiments and has a number of peculiarities. Emission from a thin plasma does not require intermediate generation of electromagnetic plasma eigenmodes, as in the infinite case, and is more similar to the regular antenna radiation. In this work, we determine how efficiently the fundamental and second harmonic emissions can be generated in previously modulated and initially homogeneous plasmas.

  17. Effect of tip geometry on photo-electron-emission from nanostructures.

    Science.gov (United States)

    Teki, Ranganath; Lu, Toh-Ming; Koratkar, Nikhil

    2009-03-01

    We show in this paper the strong effect of tip geometry on the photo-electron-emission behavior of nanostructured surfaces. To study the effect of tip geometry we compared the photo-emissivity of Ru and Pt nanorods with pyramidal shaped tips to that of carbon nanorods that display flat top (planar) tips. Flat top architectures gave no significant increase in the emission current, while nanostructures with pyramidal shaped tips showed 3-4 fold increase in photo-emission compared to a thin film of the same material. Pyramidal tip geometries increase the effective surface area that is exposed to the incident photon-flux thereby enhancing the photon-collection probability of the system. Such nano-structured surfaces show promise in a variety of device applications such as photo-detectors, photon counters and photo-multiplier tubes.

  18. Simulations of electromagnetic emissions produced in a thin plasma by a continuously injected electron beam

    Energy Technology Data Exchange (ETDEWEB)

    Annenkov, V. V. [Budker Institute of Nuclear Physics, SB RAS, 630090 Novosibirsk (Russian Federation); Timofeev, I. V.; Volchok, E. P. [Budker Institute of Nuclear Physics, SB RAS, 630090 Novosibirsk (Russian Federation); Novosibirsk State University, 630090 Novosibirsk (Russian Federation)

    2016-05-15

    In this paper, electromagnetic emissions produced in a thin beam-plasma system are studied using two-dimensional particle-in-cell simulations. For the first time, the problem of emission generation in such a system is considered in a realistic formulation allowing for the continuous injection of a relativistic electron beam through a plasma boundary. Specific attention is given to the thin plasma case in which the transverse plasma size is comparable to the typical wavelength of beam-driven oscillations. Such a case is often implemented in laboratory beam-plasma experiments and has a number of peculiarities. Emission from a thin plasma does not require intermediate generation of the electromagnetic plasma eigenmodes, as in an infinite case, and is more similar to the regular antenna radiation. In this work, we determine how efficiently the fundamental and the second harmonic emissions can be generated in previously modulated and initially homogeneous plasmas.

  19. The faint intergalactic-medium red-shifted emission balloon: future UV observations with EMCCDs

    Science.gov (United States)

    Kyne, Gillian; Hamden, Erika T.; Lingner, Nicole; Morrissey, Patrick; Nikzad, Shouleh; Martin, D. Christopher

    2016-08-01

    We present the latest developments in our joint NASA/CNES suborbital project. This project is a balloon-borne UV multi-object spectrograph, which has been designed to detect faint emission from the circumgalactic medium (CGM) around low redshift galaxies. One major change from FIREBall-1 has been the use of a delta-doped Electron Multiplying CCD (EMCCD). EMCCDs can be used in photon-counting (PC) mode to achieve extremely low readout noise (¡ 1e-). Our testing initially focused on reducing clock-induced-charge (CIC) through wave shaping and well depth optimisation with the CCD Controller for Counting Photons (CCCP) from Nüvü. This optimisation also includes methods for reducing dark current, via cooling and substrate voltage adjustment. We present result of laboratory noise measurements including dark current. Furthermore, we will briefly present some initial results from our first set of on-sky observations using a delta-doped EMCCD on the 200 inch telescope at Palomar using the Palomar Cosmic Web Imager (PCWI).

  20. Multi-Wavelength Spectroscopic Observations of a White Light Flare Produced Directly by Non-thermal Electrons

    Science.gov (United States)

    Lee, Kyoung-Sun; Imada, Shinsuke; Watanabe, Kyoko; Bamba, Yumi; Brooks, David

    2017-08-01

    An X1.6 flare on 2014 October 22 was observed by multiple spectrometers in UV, EUV and X-ray (Hinode/EIS, IRIS, and RHESSI), and multi-wavelength imaging observations (SDO/AIA and HMI). We analyze a bright kernel that produces a white light (WL) flare with continuum enhancement and a hard X-ray (HXR) peak. Taking advantage of the spectroscopic observations of IRIS and Hinode/EIS, we measure the temporal variation of the plasma properties in the bright kernel in the chromosphere and corona. We find that explosive evaporation was observed when the WL emission occurred. The temporal correlation of the WL emission, HXR peak, and evaporation flows indicates that the WL emission was produced by accelerated electrons. We calculated the energy flux deposited by non-thermal electrons (observed by RHESSI) and compared it to the dissipated energy estimated from a chromospheric line (Mg II triplet) observed by IRIS. The deposited energy flux from the non-thermal electrons is about (3-7.7)x1010 erg cm-2 s-1 for a given low-energy cutoff of 30-40 keV, assuming the thick-target model. The energy flux estimated from the changes in temperature in the chromosphere measured using the Mg II subordinate line is about (4.6-6.7)×109 erg cm-2 s-1: ˜6%-22% of the deposited energy. This comparison of estimated energy fluxes implies that the continuum enhancement was directly produced by the non-thermal electrons.

  1. A Modeling Framework for Inference of Surface Emissions Using Mobile Observations

    Science.gov (United States)

    Fasoli, B.; Mitchell, L.; Crosman, E.; Mendoza, D. L.; Lin, J. C.

    2016-12-01

    Our ability to quantify surface emissions depends on the precision of observations and the spatial density of measurement networks. Mobile measurement techniques offer a cost effective strategy for quantifying atmospheric conditions over space without requiring a dense network of in-situ sites. However, interpretation of these data and inversion of dispersed measurements to estimate surface emissions can be difficult. We introduce a framework using the Stochastic Time-Inverted Lagrangian Transport (STILT) model that assimilates both spatially resolved observations and an emissions inventory to better estimate surface fluxes. Salt Lake City is a unique laboratory for the study of urban carbon emissions. It is the only U.S. city that utilizes light-rail trains to continuously measure high frequency carbon dioxide (CO2) and methane (CH4); it is home to one of the longest and most spatially resolved high precision CO2 measurement networks (air.utah.edu); and it is one of four cities in the world for which the Hestia anthropogenic emissions inventory has been produced which characterizes CO2 emissions at the scale of individual buildings and roadways. Using these data and modeling resources, we evaluate spatially resolved CO2 measurements and transported CO2 emissions on hourly timescales at a dense spatial resolution across Salt Lake City.

  2. Controlling electronic couplings with tunable long wavelength pulses: Study of Autler-Townes splitting and XUV emission spectra

    Science.gov (United States)

    Harkema, Nathan; Liao, Chen-Ting; Sandhu, Arvinder

    2017-04-01

    Attosecond transient absorption spectroscopy (ATAS) enables the study of excited electron dynamics with unprecedented temporal and energy resolution. Many ATAS experiments use an extreme ultraviolet (XUV) pump pulse and a near-infrared (NIR) probe fixed at the fundamental laser frequency ( 800 nm) to study the light induced effects on electronic structure of atoms and molecules. We extend the technique by using an optical parametric amplifier in one arm of our setup, which allows us to independently tune the frequency of the probe pulse from 1200 to 1800 nm. These long-wavelength pulses allow us to explore a new regime, where we can control the couplings between nearby electronic states to alter the transient absorption lineshapes in atoms. We use this technique to investigate the 4p-3s detuning dependent Autler-Townes splitting of the 4p state in Helium. Light induced Floquet structures extending into the continuum are observed in our study. We demonstrate new tunable XUV emission channels from four-wave mixing processes, and the efficiency of these emissions can be strongly enhanced through resonant couplings. The tunable IR induced electronic couplings are also used to influence the autoionization dynamics in Argon. This work is supported by NSF Grant No. PHY-1505556 and ARO Grant No. W911NF-14-1-0383.

  3. Emission of low-energy electrons from multicharged ions interacting with metal surfaces

    Energy Technology Data Exchange (ETDEWEB)

    Zeijlmans van Emmichoven, P.A. (Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831-6372 (United States) Joint Institute for Heavy Ion Research, Holifield Heavy Ion Research Facility, Oak Ridge, Tennessee 37831-6374 (United States)); Havener, C.C. (Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831-6372 (United States)); Hughes, I.G. (Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831-6372 (United States) Joint Institute for Heavy Ion Research, Holifield Heavy Ion Research Facility, Oak Ridge, Tennessee 37831-6374 (United States)); Zehner, D.M.; Meyer, F.W. (Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831-6372 (United States))

    1993-05-01

    Low-energy electron spectra are reported for 60- and 100-keV multicharged ions interacting at an incident angle of 20[degree] with Au and Cu surfaces. Analysis of the spectra indicate that at least two features contribute. The first feature represents the major contribution to the total electron yield and consists of 5--10-eV electrons emitted over a wide range of angles. The angular distribution of this component is not symmetric with respect to the surface normal, but shows an increase in the forward direction of the incident ions. It will be shown that this component arises predominantly from below the surface. Possible potential-emission mechanisms which may contribute will be discussed. The second feature, which constitutes a minor part of the overall electron emission, occurs at higher electron energies ([similar to]20 eV), and is peaked at the extreme forward angles. Binary encounters between incident ions and metal electrons at the surface-vacuum interface will be shown to describe the main features of this component. At even higher electron energies ([gt]40 eV) the spectra show a tail whose slope does not depend on either the initial charge state or kinetic energy of the incident ions. The invariance with kinetic energy is in sharp contrast with the corresponding experimental results from ion-atom collisions.

  4. Complex atmospheric-lithospheric observations of acoustic emission at «Karymshina» site in Kamchatka

    Directory of Open Access Journals (Sweden)

    Larionov Igor

    2017-01-01

    Full Text Available The results of complex observations of acoustic emission in the near surface rocks and in the atmosphere by the ground surface are described. The instrumentations for the observations are a laser strainmeter-interferometer and a microbarometer installed close to each other. It was shown that during the increase of deformation rate in the near surface rocks, increase of acoustic emission intensity in the atmosphere by the ground surface is registered. The effect of meteorological factors on the observation results is evaluated.

  5. Middle East emissions of VOCs estimated using OMI HCHO observations and the MAGRITTE regional model

    Science.gov (United States)

    Müller, Jean-Francois; Stavrakou, Trisevgeni; Bauwens, Maite; De Smedt, Isabelle; Van Roozendael, Michel

    2017-04-01

    Air quality in the Middle East has considerably deteriorated in the last decades. In particular tropospheric ozone reaches very high levels during summer due to the combination of high solar irradiances with often very high and rapidly evolving anthropogenic emissions of NOx and VOCs associated to oil/gas exploitation and fast urbanisation. In addition, high biogenic VOC emissions are expected in non-desert areas, in particular during summer due to scorching temperatures and high solar irradiances. Both anthropogenic and biogenic VOC emissions are poorly known, however, due to near-absence of experimental constraints on emission factors for local vegetation and industrial and extraction processes. Furthermore, the dependence of emissions on environmental conditions (e.g. soil moisture in the case of biogenic isoprene emissions) is only very crudely parameterized in emission models. Here we use spaceborne (OMI) observations of formaldehyde, a known product of anthropogenic and biogenic VOC oxidation, as constraint in an inversion framework built on a regional model, MAGRITTE (Model of Atmospheric composition at Global and Regional scales using Inversion Techniques for Trace Gas Emissions). MAGRITTE is run at 0.5x0.5 degree resolution, with lateral boundary conditions provided by the global CTM IMAGESv2 (Bauwens et al., 2016). The global and regional models share essentially the same chemistry and physical parameterizations. Emission inversion with MAGRITTE is performed using an adjoint-based iterative procedure, similar to previous inversions using IMAGES. Biogenic VOC emissions are calculated using MEGAN (Muller et al., 2008; Stavrakou et al., 2015), whereas the HTAPv2 emission dataset is used for anthropogenic emissions, with several adjustments for oil/gas exploitation and traffic emissions. The OMI data are regridded onto the model resolution and averaged seasonally in order to reduce noise. Preliminary results indicate that biogenic isoprene emissions are a

  6. The design of a correlation electron cyclotron emission system on J-TEXT

    Energy Technology Data Exchange (ETDEWEB)

    Yang, Z. J.; Xiao, Y.; Ma, X. D.; Pan, X. M.; Xiao, J. S. [State Key Laboratory of Advanced Electromagnetic Engineering and Technology, School of Electrical and Electronic Engineering, Huazhong University of Science and Technology, Wuhan 430074 (China)

    2015-04-15

    To study the anomalous transport, a correlation electron cyclotron emission (CECE) was planned to be developed on J-TEXT for electron temperature fluctuation measurement. The spectral decorrelation method was employed for the CECE system. It was developed based on the previous 16-channel electron cyclotron emission system. They shared the optical transmission line and mixer. The CECE part consists of 4 channels. Two fixed frequency narrow band filters were used for two channels and two yttrium iron garnet (YIG) filters for the other two channels. To meet the measuring requirement, some tests have been taken for the YIG filters. The results show good performance of the filters. Gaussian optics is used to produce a good poloidal resolution. Wavenumbers resolved by the CECE diagnostic are k{sub θ} ≤ 1.5 rad/cm and k{sub r} ≤ 12 rad/cm. Some preliminary experiment results are also presented in this paper.

  7. Single-photon emission associated with double electron capture in F9+ + C collisions

    CERN Document Server

    Elkafrawy, Tamer; Tanis, John A; Warczak, Andrzej

    2016-01-01

    Radiative double electron capture (RDEC), the one-step process occurring in ion-atom collisions, has been investigated for bare fluorine ions colliding with carbon. RDEC is completed when two target electrons are captured to a bound state of a projectile simultaneously with the emission of a single photon. This work is a follow-up to our earlier measurement of RDEC for bare oxygen projectiles, thus providing a recipient system free of electron-related Coulomb fields in both cases and allowing for the comparison between the two collision systems as well as with available theoretical studies. The most significant mechanisms of x-ray emission that may contribute to the RDEC energy region as background processes are also addressed.

  8. Observations of the Prompt Optical Emission of GRB 160625B with Mini-MegaTORTORA

    Science.gov (United States)

    Karpov, S.; Beskin, G.; Biryukov, A.; Bondar, S.; Ivanov, E.; Katkova, E.; Orekhova, N.; Perkov, A.; Sasyuk, V.

    2017-06-01

    Here we report our observations of bright optical flash coincident with Fermi GRB160625B using Mini-MegaTORTORA wide-field monitoring system. The prompt optical emission is correlated with gamma one and lags behind it for about 3 seconds, that suggests that optical and gamma emission are formed in different regions of the burst. The multiwavelength properties of this burst are very similar to ones of Naked-Eye Burst, GRB080319B, we detected earlier with TORTORA camera.

  9. Biomass burning emissions estimated with a global fire assimilation system based on observed fire radiative power

    NARCIS (Netherlands)

    Kaiser, J.W.; Heil, A.; Andreae, M.O.; Benedetti, A.; Chubarova, N.; Jones, L.; Morcrette, J.J.; Razinger, M.; Schultz, M.G.; Suttie, M.; Werf, van der G.R.

    2012-01-01

    The Global Fire Assimilation System (GFASv1.0) calculates biomass burning emissions by assimilating Fire Radiative Power (FRP) observations from the MODIS instruments onboard the Terra and Aqua satellites. It corrects for gaps in the observations, which are mostly due to cloud cover, and filters

  10. Plasma electron observations in the vicinity of magnetic holes

    Science.gov (United States)

    King, J. H.; Ogilvie, K. W.; Behannon, K. W.

    1979-01-01

    In the present study, 14 events of interplanetary magnetic field dips are identified. Eleven of these are found to be associated with significant enhancements in the flux of electrons of energies of approximately 100 eV. Five (of the eleven) are characterized by significant changes in the magnetic field direction, and six are not. Thus, even though an electron enhancement is usually seen at a dip, the enhancement need not be always associated with magnetic reconnection, for which a directional change is essential. It appears that some events involve local acceleration, possibly the results of reconnection, while others may involve electrons injected onto the field line at a remote point.

  11. Gyrophase-bunched Electrons: Cluster Observations and Simulations

    Science.gov (United States)

    Gurgiolo, C.; Vinas, A. F.; Goldstein, Melvyn L.

    2003-01-01

    The interaction of the solar wind with the Earth's bow shock is responsible for a number of phenomena both upstream and downstream. One of the least understood and studied of these is the generation of gyrophase-bunched electrons. We will describe initial work searching for and analyzing such events in (Plasma Electron And Current Experiment (PEACE) data from CLUSTER. Plasma simulations will complement the data analysis. Recent analyses suggest that gyrophase-bunched electrons are present rather frequently in the upstream region, due either to energization in the reflection off the shock front or, more likely, to phase trapping in locally produced whistler wave fields.

  12. Subnanosecond breakdown development in high-voltage pulse discharge: Effect of secondary electron emission

    Science.gov (United States)

    Alexandrov, A. L.; Schweigert, I. V.; Zakrevskiy, Dm. E.; Bokhan, P. A.; Gugin, P.; Lavrukhin, M.

    2017-10-01

    A subnanosecond breakdown in high-voltage pulse discharge may be a key tool for superfast commutation of high power devices. The breakdown in high-voltage open discharge at mid-high pressure in helium was studied in experiment and in kinetic simulations. The kinetic model of electron avalanche development was constructed, based on PIC-MCC simulations, including dynamics of electrons, ions and fast helium atoms, produced by ions scattering. Special attention was paid to electron emission processes from cathode, such as: photoemission by Doppler-shifted resonant photons, produced in excitation processes involving fast atoms; electron emission by ions and fast atoms bombardment of cathode; the secondary electron emission (SEE) by hot electrons from bulk plasma. The simulations show that the fast atoms accumulation is the main reason of emission growth at the early stage of breakdown, but at the final stage, when the voltage on plasma gap diminishes, namely the SEE is responsible for subnanosecond rate of current growth. It was shown that the characteristic time of the current growth can be controlled by the SEE yield. The influence of SEE yield for three types of cathode material (titanium, SiC, and CuAlMg-alloy) was tested. By changing the pulse voltage amplitude and gas pressure, the area of existence of subnanosecond breakdown is identified. It is shown that in discharge with SiC and CuAlMg-alloy cathodes (which have enhanced SEE) the current can increase with a subnanosecond characteristic time value as small as τs = 0.4 ns, for the pulse voltage amplitude of 5÷12 kV. An increase of gas pressure from 15 Torr to 30 Torr essentially decreases the time of of current front growth, whereas the pulse voltage variation weakly affects the results.

  13. Toward observationally constrained high space and time resolution CO2 urban emission inventories

    Science.gov (United States)

    Maness, H.; Teige, V. E.; Wooldridge, P. J.; Weichsel, K.; Holstius, D.; Hooker, A.; Fung, I. Y.; Cohen, R. C.

    2013-12-01

    The spatial patterns of greenhouse gas (GHG) emission and sequestration are currently studied primarily by sensor networks and modeling tools that were designed for global and continental scale investigations of sources and sinks. In urban contexts, by design, there has been very limited investment in observing infrastructure, making it difficult to demonstrate that we have an accurate understanding of the mechanism of emissions or the ability to track processes causing changes in those emissions. Over the last few years, our team has built a new high-resolution observing instrument to address urban CO2 emissions, the BErkeley Atmospheric CO2 Observing Network (BEACON). The 20-node network is constructed on a roughly 2 km grid, permitting direct characterization of the internal structure of emissions within the San Francisco East Bay. Here we present a first assessment of BEACON's promise for evaluating the effectiveness of current and upcoming local emissions policy. Within the next several years, a variety of locally important changes are anticipated--including widespread electrification of the motor vehicle fleet and implementation of a new power standard for ships at the port of Oakland. We describe BEACON's expected performance for detecting these changes, based on results from regional forward modeling driven by a suite of projected inventories. We will further describe the network's current change detection capabilities by focusing on known high temporal frequency changes that have already occurred; examples include a week of significant freeway traffic congestion following the temporary shutdown of the local commuter rail (the Bay Area Rapid Transit system).

  14. Observation of two-dimensional longitudinal-transverse correlations in an electron beam by laser-electron interactions

    Directory of Open Access Journals (Sweden)

    G. Angelova

    2008-07-01

    Full Text Available During the preparatory work for the optical-replica synthesizer experiment in the free-electron laser FLASH at DESY, we were able to superimpose a short, approximately 200 fs long pulse from a frequency-doubled mode-locked erbium laser with titanium-sapphire amplifier and an approximately 20 ps long electron bunch in an undulator. This induces an energy modulation in a longitudinal slice of the electron bunch. A magnetic chicane downstream of the undulator converts the energy modulation into a density modulation within the slice that causes the emission of coherent optical transition radiation from a silver-coated silicon screen. Varying the relative timing between electron and laser, we use a camera to record two-dimensional images of the slices as a function of the longitudinal position within the electron bunch.

  15. Constraining Methane Emissions from Natural Gas Production in Northeastern Pennsylvania Using Aircraft Observations and Mesoscale Modeling

    Science.gov (United States)

    Barkley, Z.; Davis, K.; Lauvaux, T.; Miles, N.; Richardson, S.; Martins, D. K.; Deng, A.; Cao, Y.; Sweeney, C.; Karion, A.; Smith, M. L.; Kort, E. A.; Schwietzke, S.

    2015-12-01

    Leaks in natural gas infrastructure release methane (CH4), a potent greenhouse gas, into the atmosphere. The estimated fugitive emission rate associated with the production phase varies greatly between studies, hindering our understanding of the natural gas energy efficiency. This study presents a new application of inverse methodology for estimating regional fugitive emission rates from natural gas production. Methane observations across the Marcellus region in northeastern Pennsylvania were obtained during a three week flight campaign in May 2015 performed by a team from the National Oceanic and Atmospheric Administration (NOAA) Global Monitoring Division and the University of Michigan. In addition to these data, CH4 observations were obtained from automobile campaigns during various periods from 2013-2015. An inventory of CH4 emissions was then created for various sources in Pennsylvania, including coalmines, enteric fermentation, industry, waste management, and unconventional and conventional wells. As a first-guess emission rate for natural gas activity, a leakage rate equal to 2% of the natural gas production was emitted at the locations of unconventional wells across PA. These emission rates were coupled to the Weather Research and Forecasting model with the chemistry module (WRF-Chem) and atmospheric CH4 concentration fields at 1km resolution were generated. Projected atmospheric enhancements from WRF-Chem were compared to observations, and the emission rate from unconventional wells was adjusted to minimize errors between observations and simulation. We show that the modeled CH4 plume structures match observed plumes downwind of unconventional wells, providing confidence in the methodology. In all cases, the fugitive emission rate was found to be lower than our first guess. In this initial emission configuration, each well has been assigned the same fugitive emission rate, which can potentially impair our ability to match the observed spatial variability

  16. New results of structured VLF emissions observed simultaneously at two closely located stations near L ~ 5.5

    Directory of Open Access Journals (Sweden)

    J. Manninen

    2014-09-01

    Full Text Available Simultaneous records of VLF (very low frequencies emissions have been carried out at two ground-based stations located at similar geomagnetic latitudes near L ~ 5.5 and spaced in the longitude by ~ 400 km, Kannuslehto (KAN in Finland and Lovozero (LOZ in Russia, using quite similar VLF receivers with two calibrated orthogonal air-core loop antennas. We found that the general spectral properties of the VLF chorus emissions at these two stations were similar and typically have right-hand polarization. Contrary to VLF chorus, the short-period VLF emissions (periodic emissions, PE in which separated spectral elements are repeated with the periodicity of 3–4 s were mostly left-hand polarized. Usually, these waves propagated in the north–south direction. We suppose that PEs are generated inside of the plasmasphere by the cyclotron instability under a quasi-linear relaxation of the energetic electron distribution function. However, sometimes PE occurred only at an individual station. We speculated that this could be due to the influence of the local inhomogeneities to the VLF waves during the propagation through the ionospheric trough to the ground. Unusual series of short-duration (10–100 s bursts of VLF emissions, lasting several hours, were also found in the morning under very quiet geomagnetic conditions (Kp ~ 0–1. Generally, these emissions were observed simultaneously at KAN and LOZ showing both right-hand and left-hand polarization, and different arrival directions provided the rather extended ionospheric exit area.

  17. Enhanced field electron emission of graphene sheets by CsI coating after electrophoretic deposition.

    Science.gov (United States)

    Liu, Jianlong; Zeng, Baoqing; Wu, Zhe; Sun, Hao

    2012-03-01

    Because of the large quantities of edges, graphene can serve as an efficient edge emitter for field emission (FE). Cesium iodide (CsI) coating was promising to enhance the electron emission and utilized in FE applications. In this work, FE of graphene sheets after electrophoretic deposition (ED) was studied. Electron emission property of GS was obviously improved by coating with CsI. The turn-on field of GS decreased from 4.4 to 2.5 V/ μm; and threshold field decreased from 9 to 5.8 V/μm, respectively. This FE improvement must due to a higher effective density of emission site generated around the GS surface after coating. Scanning electron microscopy (SEM) and computation were taken to reveal the influence after coating. Investigations of CsI coated MWCNTs were also compared in order to better understand the origin of the low turn-on electric field obtained by GS. © 2012 American Chemical Society

  18. Comparison of seasonal variation between anthropogenic and natural emission inventory and Satellite observation in Southeast Asia

    Science.gov (United States)

    Kurata, G.; Lalitaporn, P.

    2012-12-01

    Since the economic growth of the countries in Southeast Asia is significantly rapid, the emission of air pollutant from the anthropogenic activity, such as industry, power generation and transportation is rapidly increasing. Moreover, biomass burning due to unsuitable agricultural management, deforestation and expansion of farmland are discharging large amount of pollutants, such as Carbon monoxide, volatile organic compound and particulate matter. Especially, the particulate matter from biomass burning causes the serious haze pollution in surrounding area in Southeast Asia. Furthermore, the biomass fuel used for cooking at residential sector discharges harmful pollutants including a particulate matter, and causes the adverse health impact to people on indoor and outdoor. In this study, we evaluated the spatial distribution and the seasonal variation of emission inventory for Southeast Asia region by comparing with satellite observation data in order to improve the accuracy of the impact assessment of air pollution by regional atmospheric chemistry transport model (WRF and CMAQ). As an emission inventory data, we used our original regional emission inventory for Southeast Asia region developed from detail transportation and industry data sets as well as a several existing emission inventories. As satellite observation data, the vertical column density of NO2, Particulate matter and Carbon monoxide obtained by various satellite, such as GOME, GOME2, SCIAMACY, OMI and so on. As a result of comparisons between satellite observation and emission inventories from 1996 to 2011, in the case of anthropogenic emission, seasonal variation was comparatively well in agreement with the seasonal variation of satellite data. However, the uncertainty of the seasonal variation was large on several large cities. In the case of emission from biomass burning, the seasonal variation was clear, but inter-annual variation was also large due to large scale climate condition.

  19. Strategies and results of field emission scanning electron microscopy (FE-SEM) in the study of parasitic protozoa.

    Science.gov (United States)

    de Souza, Wanderley; Campanati, Loraine; Attias, Marcia

    2008-01-01

    Field emission scanning electron microscopy (FE-SEM) provides a range of strategies for investigating the structural organization of biological systems, varying from isolated macromolecules to tissue organization and whole organisms. This review covers some of the results so far obtained using FE-SEM observation and various protocols of sample fixation to analyze the structural organization of parasitic protozoa and their interaction with host cells. The employment of FE-SEM can be broadened through the use of gold-labeled molecules or tracers, gradual extraction by detergents, and cleavage techniques. These analyses provide significant contributions to the characterization of these organisms concerning ultrastructure, cytoskeleton, motility and intracellular behavior.

  20. Ranges, Reflection and Secondary Electron Emission for keV Hydrogen Ions Incident on Solid N2

    DEFF Research Database (Denmark)

    Børgesen, P.; Sørensen, H.; Hao-Ming, Chen

    1983-01-01

    Ranges were measured for 0.67–3.3 keV/amu hydrogen and deuterium ions in solid N2. Comparisons with similar results for N2-gas confirm the previously observed large phase effect in the stopping cross section. Measurements of the secondary electron emission coefficient for bulk solid N2 bombarded...... by 0.67–9 keV/amu ions also seem to support such a phase effect. It is argued that we may also extract information about the charge state of reflected projectiles....

  1. Profile and Morphology of Fungal Aerosols Characterized by Field Emission Scanning Electron Microscopy (FESEM).

    Science.gov (United States)

    Afanou, Komlavi Anani; Straumfors, Anne; Skogstad, Asbjørn; Skaar, Ida; Hjeljord, Linda; Skare, Øivind; Green, Brett James; Tronsmo, Arne; Eduard, Wijnand

    Fungal aerosols consist of spores and fragments with diverse array of morphologies; however, the size, shape, and origin of the constituents require further characterization. In this study, we characterize the profile of aerosols generated from Aspergillus fumigatus, A. versicolor, and Penicillium chrysogenum grown for 8 weeks on gypsum boards. Fungal particles were aerosolized at 12 and 20 L min-1 using the Fungal Spore Source Strength Tester (FSSST) and the Stami particle generator (SPG). Collected particles were analyzed with field emission scanning electron microscopy (FESEM). We observed spore particle fraction consisting of single spores and spore aggregates in four size categories, and a fragment fraction that contained submicronic fragments and three size categories of larger fragments. Single spores dominated the aerosols from A. fumigatus (median: 53%), while the submicronic fragment fraction was the highest in the aerosols collected from A. versicolor (median: 34%) and P. chrysogenum (median: 31%). Morphological characteristics showed near spherical particles that were only single spores, oblong particles that comprise some spore aggregates and fragments (3.5 μm). Further, the near spherical particles dominated the aerosols from A. fumigatus (median: 53%), while oblong particles were dominant in the aerosols from A. versicolor (68%) and P. chrysogenum (55%). Fiber-like particles represented 21% and 24% of the aerosols from A. versicolor and P. chrysogenum, respectively. This study shows that fungal particles of various size, shape, and origin are aerosolized, and supports the need to include a broader range of particle types in fungal exposure assessment.

  2. Attosecond interferometry with self-amplified spontaneous emission of a free-electron laser

    Science.gov (United States)

    Usenko, Sergey; Przystawik, Andreas; Jakob, Markus Alexander; Lazzarino, Leslie Lamberto; Brenner, Günter; Toleikis, Sven; Haunhorst, Christian; Kip, Detlef; Laarmann, Tim

    2017-05-01

    Light-phase-sensitive techniques, such as coherent multidimensional spectroscopy, are well-established in a broad spectral range, already spanning from radio-frequencies in nuclear magnetic resonance spectroscopy to visible and ultraviolet wavelengths in nonlinear optics with table-top lasers. In these cases, the ability to tailor the phases of electromagnetic waves with high precision is essential. Here we achieve phase control of extreme-ultraviolet pulses from a free-electron laser (FEL) on the attosecond timescale in a Michelson-type all-reflective interferometric autocorrelator. By varying the relative phase of the generated pulse replicas with sub-cycle precision we observe the field interference, that is, the light-wave oscillation with a period of 129 as. The successful transfer of a powerful optical method towards short-wavelength FEL science and technology paves the way towards utilization of advanced nonlinear methodologies even at partially coherent soft X-ray FEL sources that rely on self-amplified spontaneous emission.

  3. Constraining Swiss Methane Emissions from Atmospheric Observations: Sensitivities and Temporal Development

    Science.gov (United States)

    Henne, Stephan; Leuenberger, Markus; Steinbacher, Martin; Eugster, Werner; Meinhardt, Frank; Bergamaschi, Peter; Emmenegger, Lukas; Brunner, Dominik

    2017-04-01

    Similar to other Western European countries, agricultural sources dominate the methane (CH4) emission budget in Switzerland. 'Bottom-up' estimates of these emissions are still connected with relatively large uncertainties due to considerable variability and uncertainties in observed emission factors for the underlying processes (e.g., enteric fermentation, manure management). Here, we present a regional-scale (˜300 x 200 km2) atmospheric inversion study of CH4 emissions in Switzerland making use of the recently established CarboCount-CH network of four stations on the Swiss Plateau as well as the neighbouring mountain-top sites Jungfraujoch and Schauinsland (Germany). Continuous observations from all CarboCount-CH sites are available since 2013. We use a high-resolution (7 x 7 km2) Lagrangian particle dispersion model (FLEXPART-COSMO) in connection with two different inversion systems (Bayesian and extended Kalman filter) to estimate spatially and temporally resolved CH4 emissions for the Swiss domain in the period 2013 to 2016. An extensive set of sensitivity inversions is used to assess the overall uncertainty of our inverse approach. In general we find good agreement of the total Swiss CH4 emissions between our 'top-down' estimate and the national 'bottom-up' reporting. In addition, a robust emission seasonality, with reduced winter time values, can be seen in all years. No significant trend or year-to-year variability was observed for the analysed four-year period, again in agreement with a very small downward trend in the national 'bottom-up' reporting. Special attention is given to the influence of boundary conditions as taken from different global scale model simulations (TM5, FLEXPART) and remote observations. We find that uncertainties in the boundary conditions can induce large offsets in the national total emissions. However, spatial emission patterns are less sensitive to the choice of boundary condition. Furthermore and in order to demonstrate the

  4. Visible-infrared self-amplified spontaneous emission amplifier free electron laser undulator

    Directory of Open Access Journals (Sweden)

    Roger Carr

    2001-12-01

    Full Text Available The visible-infrared self-amplified spontaneous emission amplifier (VISA free electron laser (FEL is an experimental device designed to show self-amplified spontaneous emission (SASE to saturation in the near infrared to visible light energy range. It generates a resonant wavelength output from 800–600 nm, so that silicon detectors may be used to characterize the optical properties of the FEL radiation. VISA is designed to show how SASE FEL theory corresponds with experiment in this wavelength range, using an electron beam with emittance close to that planned for the future Linear Coherent Light Source at SLAC. VISA comprises a 4 m pure permanent magnet undulator with four 99 cm segments, each of 55 periods, 18 mm long. The undulator has distributed focusing built into it, to reduce the average beta function of the 70–85 MeV electron beam to about 30 cm. There are four FODO cells per segment. The permanent magnet focusing lattice consists of blocks mounted on either side of the electron beam, in the undulator gap. The most important undulator error parameter for a free electron laser is the trajectory walk-off, or lack of overlap of the photon and electron beams. Using pulsed wire magnet measurements and magnet shimming, we were able to control trajectory walk-off to less than ±50 μm per field gain length.

  5. Reply to ``Comment on `Imaging the atomic orbitals of carbon atomic chains with field-emission electron microscopy' ''

    Science.gov (United States)

    Mikhailovskij, I. M.; Sadanov, E. V.; Mazilova, T. I.; Ksenofontov, V. A.; Velicodnaja, O. A.

    2010-03-01

    In our recent paper [I. M. Mikhailovskij, E. V. Sadanov, T. I. Mazilova, V. A. Ksenofontov, and O. A. Velicodnaja, Phys. Rev. B 80, 165404 (2009)], we have presented evidence for field emission from individual orbitals of self-standing carbon chains, which can be used for real-space imaging of the end-atom orbitals with a field-emission electron microscope (FEEM). In this reply to the preceding Comment, we refer to the issues brought up there, which concern the viewpoint that the observed spontaneous mutual transformations of FEEM patterns have been attributed to the ligand-induced symmetry breaking by calling attention to the role of hydrogen atoms unavoidable in most nanostructured carbon materials.

  6. Effect of secondary electron emission on subnanosecond breakdown in high-voltage pulse discharge

    Science.gov (United States)

    Schweigert, I. V.; Alexandrov, A. L.; Gugin, P.; Lavrukhin, M.; Bokhan, P. A.; Zakrevsky, Dm E.

    2017-11-01

    The subnanosecond breakdown in open discharge may be applied for producing superfast high power switches. Such fast breakdown in high-voltage pulse discharge in helium was explored both in experiment and in kinetic simulations. The kinetic model of electron avalanche development was developed using PIC-MCC technique. The model simulates motion of electrons, ions and fast helium atoms, appearing due to ions scattering. It was shown that the mechanism responsible for ultra-fast breakdown development is the electron emission from cathode. The photoemission and emission by ions or fast atoms impact is the main reason of current growth at the early stage of breakdown, but at the final stage, when the voltage on discharge gap drops, the secondary electron emission (SEE) is responsible for subnanosecond time scale of current growth. It was also found that the characteristic time of the current growth τS depends on the SEE yield of the cathode material. Three types of cathode material (titanium, SiC, and CuAlMg-alloy) were tested. It is shown that in discharge with SiC and CuAlMg-alloy cathodes (which have enhanced SEE) the current can increase with a subnanosecond characteristic time as small as τS = 0.4 ns, for the pulse voltage amplitude of 5- 12 kV..

  7. Estimation of NOx emissions from NO2 hotspots in polluted background using satellite observations

    Science.gov (United States)

    Liu, Fei; Beirle, Steffen; Zhang, Qiang; Wagner, Thomas

    2015-04-01

    Satellite observations have been widely used to study NOx emissions from power plants and cities, which are major NOx sources with large impacts on human health and climate. The quantification of NOx emissions from measured column densities of NO2 requires information on the NOx lifetime, which is typically gained from atmospheric chemistry models. But some recent studies determined the NOx lifetime from the satellite observations as well by analyzing the downwind plume evolution; however, this approach was so far only applied for strong isolated 'point sources' located in clean background, like Riyadh in Saudi Arabia. Here we present a modified method for the quantification of NOx emissions and corresponding atmospheric lifetimes based on OMI observations of NO2, together with ECMWF wind fields, but without further model input, for hot spots located in polluted background. We use the observed NO2 patterns under calm wind conditions as proxy for the spatial patterns of NOx emissions; by this approach, even complex source distributions can be treated realistically. From the change of the spatial patterns of NO2 at larger wind speeds (separately for different wind directions), the effective atmospheric lifetime is fitted. Emissions are derived from integrated NO2 columns above background by division by the corresponding lifetime. NOx lifetimes and emissions are estimated for 19 power plants and 50 cities across China and the US. The derived lifetimes are 3.3 ± 1.2 hours on average with extreme values of 0.9 to 7.7 hours. The resulting very short lifetimes for mountainous sites have been found to be uncertain due to the potentially inaccurate ECMWF wind data in mountainous regions. The derived NOx emissions show overall good agreement with bottom-up inventories.

  8. Short-term observations of double peaked Na emission from Mercury's exosphere

    Science.gov (United States)

    Massetti, Stefano; Mangano, Valeria; Milillo, Anna; Mura, Alessandro; Orsini, Stefano; Plainaki, Christina

    2017-04-01

    Analysis of a sequence of short-term ground-based observations of the Na emission from the exosphere of Mercury, recorded during three consecutive days (June 7-9, 2012), is presented. We observed a stable double-peak pattern where the exospheric Na emission was confined close to the nominal magnetospheric cusp footprints. During a series of scheduled observations of the global Na emission from the THEMIS telescope, achieved by scanning the whole planet's disc, we performed some extra measurements by recording the Na emission from a narrow North-South strip only, centred above the two Na emission peaks. When possible, these complementary measurements were recorded when the NASA Messenger spacecraft, orbiting around Mercury, was outside the planet's magnetosphere, in order to have contemporary in-situ data of the unperturbed interplanetary magnetic field. Our aim was to inspect the existence of short-term variabilities, which were never been reported before from ground-based observations, and their possible relationship with IMF variations. In spite of the fact that Mercury possess a miniature magnetosphere, characterized by fast reconnection events that develops on a timescale of few minutes (1-3 min), ground-based observations show that the exospheric Na emission pattern can be globally stable for a very prolonged period (some days), but it seems it can also shows variations in the time range of tens of minutes. In specific, we observed a decrease of the South/North ratio due to the decrease of the Na release from the southern cusp with respect to the northern one. This event lasted for about one hour, within several minor in-phase variations that involved both hemispheres.

  9. Validation of the Swiss methane emission inventory by atmospheric observations and inverse modelling

    Directory of Open Access Journals (Sweden)

    S. Henne

    2016-03-01

    Full Text Available Atmospheric inverse modelling has the potential to provide observation-based estimates of greenhouse gas emissions at the country scale, thereby allowing for an independent validation of national emission inventories. Here, we present a regional-scale inverse modelling study to quantify the emissions of methane (CH4 from Switzerland, making use of the newly established CarboCount-CH measurement network and a high-resolution Lagrangian transport model. In our reference inversion, prior emissions were taken from the "bottom-up" Swiss Greenhouse Gas Inventory (SGHGI as published by the Swiss Federal Office for the Environment in 2014 for the year 2012. Overall we estimate national CH4 emissions to be 196 ± 18 Gg yr−1 for the year 2013 (1σ uncertainty. This result is in close agreement with the recently revised SGHGI estimate of 206 ± 33 Gg yr−1 as reported in 2015 for the year 2012. Results from sensitivity inversions using alternative prior emissions, uncertainty covariance settings, large-scale background mole fractions, two different inverse algorithms (Bayesian and extended Kalman filter, and two different transport models confirm the robustness and independent character of our estimate. According to the latest SGHGI estimate the main CH4 source categories in Switzerland are agriculture (78 %, waste handling (15 % and natural gas distribution and combustion (6 %. The spatial distribution and seasonal variability of our posterior emissions suggest an overestimation of agricultural CH4 emissions by 10 to 20 % in the most recent SGHGI, which is likely due to an overestimation of emissions from manure handling. Urban areas do not appear as emission hotspots in our posterior results, suggesting that leakages from natural gas distribution are only a minor source of CH4 in Switzerland. This is consistent with rather low emissions of 8.4 Gg yr−1 reported by the SGHGI but inconsistent with the much higher value of 32 Gg yr−1 implied by the

  10. Global auroral conductance distribution due to electron and proton precipitation from IMAGE-FUV observations

    Directory of Open Access Journals (Sweden)

    V. Coumans

    2004-04-01

    Full Text Available The Far Ultraviolet (FUV imaging system on board the IMAGE satellite provides a global view of the north auroral region in three spectral channels, including the SI12 camera sensitive to Doppler shifted Lyman-α emission. FUV images are used to produce instantaneous maps of electron mean energy and energy fluxes for precipitated protons and electrons. We describe a method to calculate ionospheric Hall and Pedersen conductivities induced by auroral proton and electron ionization based on a model of interaction of auroral particles with the atmosphere. Different assumptions on the energy spectral distribution for electrons and protons are compared. Global maps of ionospheric conductances due to instantaneous observation of precipitating protons are calculated. The contribution of auroral protons in the total conductance induced by both types of auroral particles is also evaluated and the importance of proton precipitation is evaluated. This method is well adapted to analyze the time evolution of ionospheric conductances due to precipitating particles over the auroral region or in particular sectors. Results are illustrated with conductance maps of the north polar region obtained during four periods with different activity levels. It is found that the proton contribution to conductance is relatively higher during quiet periods than during substorms. The proton contribution is higher in the period before the onset and strongly decreases during the expansion phase of substorms. During a substorm which occurred on 28 April 2001, a region of strong proton precipitation is observed with SI12 around 14:00MLT at ~75° MLAT. Calculation of conductances in this sector shows that neglecting the protons contribution would produce a large error. We discuss possible effects of the proton precipitation on electron precipitation in auroral arcs. The increase in the ionospheric conductivity, induced by a former proton precipitation can reduce the potential drop

  11. Global auroral conductance distribution due to electron and proton precipitation from IMAGE-FUV observations

    Directory of Open Access Journals (Sweden)

    V. Coumans

    2004-04-01

    Full Text Available The Far Ultraviolet (FUV imaging system on board the IMAGE satellite provides a global view of the north auroral region in three spectral channels, including the SI12 camera sensitive to Doppler shifted Lyman-α emission. FUV images are used to produce instantaneous maps of electron mean energy and energy fluxes for precipitated protons and electrons. We describe a method to calculate ionospheric Hall and Pedersen conductivities induced by auroral proton and electron ionization based on a model of interaction of auroral particles with the atmosphere. Different assumptions on the energy spectral distribution for electrons and protons are compared. Global maps of ionospheric conductances due to instantaneous observation of precipitating protons are calculated. The contribution of auroral protons in the total conductance induced by both types of auroral particles is also evaluated and the importance of proton precipitation is evaluated. This method is well adapted to analyze the time evolution of ionospheric conductances due to precipitating particles over the auroral region or in particular sectors. Results are illustrated with conductance maps of the north polar region obtained during four periods with different activity levels. It is found that the proton contribution to conductance is relatively higher during quiet periods than during substorms. The proton contribution is higher in the period before the onset and strongly decreases during the expansion phase of substorms. During a substorm which occurred on 28 April 2001, a region of strong proton precipitation is observed with SI12 around 14:00MLT at ~75° MLAT. Calculation of conductances in this sector shows that neglecting the protons contribution would produce a large error. We discuss possible effects of the proton precipitation on electron precipitation in auroral arcs. The increase in the ionospheric conductivity, induced by a former proton precipitation can reduce the potential drop

  12. A multi-scale comparison of modeled and observed seasonal methane emissions in northern wetlands

    Science.gov (United States)

    Xu, Xiyan; Riley, William J.; Koven, Charles D.; Billesbach, Dave P.; Chang, Rachel Y.-W.; Commane, Róisín; Euskirchen, Eugénie S.; Hartery, Sean; Harazono, Yoshinobu; Iwata, Hiroki; McDonald, Kyle C.; Miller, Charles E.; Oechel, Walter C.; Poulter, Benjamin; Raz-Yaseef, Naama; Sweeney, Colm; Torn, Margaret; Wofsy, Steven C.; Zhang, Zhen; Zona, Donatella

    2016-09-01

    Wetlands are the largest global natural methane (CH4) source, and emissions between 50 and 70° N latitude contribute 10-30 % to this source. Predictive capability of land models for northern wetland CH4 emissions is still low due to limited site measurements, strong spatial and temporal variability in emissions, and complex hydrological and biogeochemical dynamics. To explore this issue, we compare wetland CH4 emission predictions from the Community Land Model 4.5 (CLM4.5-BGC) with site- to regional-scale observations. A comparison of the CH4 fluxes with eddy flux data highlighted needed changes to the model's estimate of aerenchyma area, which we implemented and tested. The model modification substantially reduced biases in CH4 emissions when compared with CarbonTracker CH4 predictions. CLM4.5 CH4 emission predictions agree well with growing season (May-September) CarbonTracker Alaskan regional-level CH4 predictions and site-level observations. However, CLM4.5 underestimated CH4 emissions in the cold season (October-April). The monthly atmospheric CH4 mole fraction enhancements due to wetland emissions are also assessed using the Weather Research and Forecasting-Stochastic Time-Inverted Lagrangian Transport (WRF-STILT) model coupled with daily emissions from CLM4.5 and compared with aircraft CH4 mole fraction measurements from the Carbon in Arctic Reservoirs Vulnerability Experiment (CARVE) campaign. Both the tower and aircraft analyses confirm the underestimate of cold-season CH4 emissions by CLM4.5. The greatest uncertainties in predicting the seasonal CH4 cycle are from the wetland extent, cold-season CH4 production and CH4 transport processes. We recommend more cold-season experimental studies in high-latitude systems, which could improve the understanding and parameterization of ecosystem structure and function during this period. Predicted CH4 emissions remain uncertain, but we show here that benchmarking against observations across spatial scales can

  13. A High-Resolution Study of Quasiperiodic Radio Emissions Observed by the Galileo Plasma Wave Instrument

    Science.gov (United States)

    Menietti, J. D.; Christopher, I.; Granroth, L. J.

    2001-01-01

    We have conducted a study of quasiperiodic emission observed by the plasma wave instrument on board the Galileo spacecraft. These emissions appear as broadband bursts with dominant periods ranging from 10 min to over 40 min. For these emissions we have explicitly analyzed the high-resolution (waveform) data to determine the presence of impulsive, solitary signatures. Our investigations have indicated that the broadband bursts, as well as the background more narrowband continuum emission, are composed of a highly turbulent spectrum. Within the broadband burst, however, there are higher-frequency components present, but no impulsive electrostatic signatures. Also significantly, the broadband bursts show no low-frequency dispersion. We conclude that the bursts are consistent with a distant, electromagnetic source, probably in the near-Jupiter vicinity.

  14. Indirect Band Gap Emission by Hot Electron Injection in Metal/MoS₂ and Metal/WSe₂ Heterojunctions.

    Science.gov (United States)

    Li, Zhen; Ezhilarasu, Goutham; Chatzakis, Ioannis; Dhall, Rohan; Chen, Chun-Chung; Cronin, Stephen B

    2015-06-10

    Transition metal dichalcogenides (TMDCs), such as MoS2 and WSe2, are free of dangling bonds and therefore make more "ideal" Schottky junctions than bulk semiconductors, which produce Fermi energy pinning and recombination centers at the interface with bulk metals, inhibiting charge transfer. Here, we observe a more than 10× enhancement in the indirect band gap photoluminescence of transition metal dichalcogenides (TMDCs) deposited on various metals (e.g., Cu, Au, Ag), while the direct band gap emission remains unchanged. We believe the main mechanism of light emission arises from photoexcited hot electrons in the metal that are injected into the conduction band of MoS2 and WSe2 and subsequently recombine radiatively with minority holes in the TMDC. Since the conduction band at the K-point is 0.5 eV higher than at the Σ-point, a lower Schottky barrier exists for the Σ-point band, making electron injection more favorable. Also, the Σ band consists of the sulfur pz orbital, which overlaps more significantly with the electron wave functions in the metal. This enhancement in the indirect emission only occurs for thick flakes of MoS2 and WSe2 (≥100 nm) and is completely absent in monolayer and few-layer (∼10 nm) flakes. Here, the flake thickness must exceed the depletion width of the Schottky junction, in order for efficient radiative recombination to occur in the TMDC. The intensity of this indirect peak decreases at low temperatures, which is consistent with the hot electron injection model.

  15. First observation of {sup 54}Zn and its decay by two-proton emission

    Energy Technology Data Exchange (ETDEWEB)

    Blank, B.; Bey, A.; Canchel, G.; Dossat, C.; Fleury, A.; Giovinazzo, J. [Le Haut Vigneau, CENBG, Gradignan Cedex (France); Adimi, N. [Faculte de Physique, USTHB, Alger (Algeria); Matea, I. [Le Haut Vigneau, CENBG, Gradignan Cedex (France); Grand Accelerateur National d' Ions Lourds, Caen Cedex (France); De Oliveira, F.; Stefan, I.; Geogiev, G.; Grevy, S.; Thomas, J.C. [Grand Accelerateur National d' Ions Lourds, Caen Cedex (France); Borcea, C. [Institute of Atomic Physics, Bucharest-Margurele (Romania); Cortina, D.; Caamano, M. [Universidad de Santiago de Compostela, Departamento de Fisica de Particulas, Santiago de Compostela (Spain); Stanoiu, M. [Institut de Physique Nucleaire d' Orsay (France); Aksouh, F. [Instituut voor Kern- en Stralingsfysica, Leuven (Belgium)

    2005-09-01

    In an experiment performed at the LISE3 facility of GANIL, the isotope {sup 54}Zn and its decay via two-proton emission were observed for the first time. In addition, preliminary results indicate that three implantation events of {sup 48}Ni were observed. One of the associated decay events is compatible with a two-proton emission. New data on the decay of {sup 45}Fe and its two-proton branch were recorded at the same time. The results for {sup 54}Zn are compared to theory. (orig.)

  16. Estimation of Swiss methane emissions by near surface observations and inverse modeling

    Science.gov (United States)

    Henne, Stephan; Brian, Oney; Leuenberger, Markus; Bamberger, Ines; Eugster, Werner; Steinbacher, Martin; Meinhardt, Frank; Brunner, Dominik

    2015-04-01

    On a global scale methane (CH4) is the second most important long-lived greenhouse gas. It is released from both natural and anthropogenic processes and its atmospheric burden has more than doubled since preindustrial times. Current CH4 emission estimates are associated with comparatively large uncertainties both globally and regionally. For example, the Swiss national greenhouse gas inventory assigns an uncertainty of 18% to the country total anthropogenic CH4 emissions as compared to only 3% for anthropogenic CO2 emissions. In Switzerland, CH4 is thought to be mainly released by agricultural activities (ruminants and manure management >80%), while natural emissions from wetlands and wild animals represent a minor source (~3 %). The country total and especially the spatial distribution of CH4 emission within Switzerland strongly differs between the national and different European scale inventories. To validate the 'bottom-up' Swiss CH4 emission estimate and to reduce its uncertainty both in total and spatially, 'top-down' methods combining atmospheric CH4 observations and regional scale transport simulations can be used. Here, we analyse continuous, near surface observations of CH4 concentrations as collected within the newly established CarboCountCH measurement network (http://www.carbocount.ch). The network consists of 4 sites situated on the Swiss Plateau, comprising a tall tower site (217 m), two elevated (mountaintop) sites and a small tower site (32 m) in flat terrain. In addition, continuous CH4 observations from the nearby high-altitude site Jungfraujoch (Alps) and the mountaintop site Schauinsland (Germany) were used. Two inversion frameworks were applied to the CH4 observations in combination with source sensitivities (footprints) calculated with the regional scale version of the Lagrangian Particle Dispersion Model FLEXPART. One inversion system was based on a Bayesian framework, while the other utilized an extended Kalman filter approach. The transport

  17. Enhanced THz emission from c-plane InxGa1-xN due to piezoelectric field-induced electron transport

    Science.gov (United States)

    Woodward, Nathaniel; Gallinat, C.; Rodak, L. E.; Metcalfe, G. D.; Shen, H.; Wraback, M.

    2012-05-01

    Enhanced terahertz emission from coherently strained InxGa1-xN epilayers on GaN is observed, which exceeds or is comparable to bulk InAs emission at pump wavelengths of 400 nm or 800 nm, respectively. The inverted terahertz waveform from the InxGa1-xN/GaN heterostructure indicates that the dominant terahertz generation mechanism is electron acceleration toward the InxGa1-xN surface in an internal electric field primarily associated with piezoelectric polarization charge at the heterointerface, rather than diffusive transport away from the surface typically observed in bulk semiconductors. The persistence of the inverted waveform for 266 nm excitation provides evidence of ultrafast electron relaxation via LO phonon emission.

  18. Fine spectral structures in Jovian decametric radio emission observed by ground-based radio telescope.

    Science.gov (United States)

    Panchenko, M.; Brazhenko, A. I.; Shaposhnikov, V. E.; Konovalenko, A. A.; Rucker, H. O.

    2014-04-01

    Jupiter with the largest planetary magnetosphere in the solar system emits intense coherent non-thermal radio emission in a wide frequency range. This emission is a result of a complicated interaction between the dynamic Jovian magnetosphere and energetic particles supplying the free energy from planetary rotation and the interaction between Jupiter and the Galilean moons. Decametric radio emission (DAM) is the strongest component of Jovian radiation observed in a frequency range from few MHz up to 40 MHz. This emission is generated via cyclotron maser mechanism in sources located along Jovian magnetic field lines. Depending on the time scales the Jovian DAMexhibits different complex spectral structures. We present the observations of the Jovian decametric radio emission using the large ground-based radio telescope URAN- 2 (Poltava, Ukraine) operated in the decametric frequency range. This telescope is one of the largest low frequency telescopes in Europe equipped with high performance digital radio spectrometers. The antenna array of URAN-2 consists of 512 crossed dipoles with an effective area of 28 000m2 and beam pattern size of 3.5 x 7 deg. (at 25 MHz). The instrument enables continuous observations of the Jovian radio during long period of times. Jovian DAM was observed continuously since Sep. 2012 (depending on Jupiter visibility) with relatively high time-frequency resolution (4 kHz - 100ms) in the broad frequency range (8-32MHz). We have detected a big amount of the fine spectral structures in the dynamic spectra of DAM such as trains of S-bursts, quasi-continuous narrowband emission, narrow-band splitting events and zebra stripe-like patterns. We analyzed mainly the fine structures associated with non-Io controlled DAM. We discuss how the observed narrowband structures which most probably are related to the propagation of the decametric radiation in the Jupiter's ionosphere can be used to study the plasma parameters in the inner Jovian magnetosphere.

  19. Electron emission yield and charging process of alkali-silicate glass submitted to an electron beam under the varying temperature condition

    Energy Technology Data Exchange (ETDEWEB)

    Belhaj, M., E-mail: Mohamed.Belhaj@onera.fr [ONERA - French Aerospace Lab, F-31055 Toulouse (France); Tondu, T.; Inguimbert, V. [ONERA - French Aerospace Lab, F-31055 Toulouse (France); Elsafi, B.; Fakhfakh, S. [LaMaCop, Faculte des Sciences de SFAX, Route Soukra Km 3, BP 1171, C.P 3000 Sfax (Tunisia); Jbara, O., E-mail: omar.jbara@univ-reims.fr [GRESPI/Materiaux Fonctionnels, UFR Sciences, BP 1039, 51687 Reims Cedex 2 (France)

    2012-01-01

    The electron emission due to electron impact of alkali-silicate glasses is measured with a technique based on the use of a Kelvin probe (KP method) and a pulsed electron beam. The KP method, allows a clear discrimination between the external and internal effects of charging process. The effect of the incident charge fluence, incident charge fluency and the temperature on the yield curve is investigated. It was found that, at room temperature as well as at 80 Degree-Sign C, electron emission varies with charge fluence. The effects of the temperature on charging mechanisms and charge transport characteristics of alkali-silicate glasses where also studied using the measurement of displacement and leakage currents under continuous electron irradiation in scanning electron microscope (SEM). The results clearly establish a correlation between charge carriers mobility and secondary electron emission yield. The enhancement of charge carrier mobility with increasing the temperature prevents the formation of a positive space charge (i.e. creation of positive ions and/or holes) that internally reduces the secondary electron (SE) emission. The higher is the temperature and the higher is the electron emission yield (EEY).

  20. Can the envisaged reductions of fossil fuel CO2 emissions be detected by atmospheric observations?

    Science.gov (United States)

    Levin, Ingeborg; Rödenbeck, Christian

    2008-03-01

    The lower troposphere is an excellent receptacle, which integrates anthropogenic greenhouse gases emissions over large areas. Therefore, atmospheric concentration observations over populated regions would provide the ultimate proof if sustained emissions changes have occurred. The most important anthropogenic greenhouse gas, carbon dioxide (CO(2)), also shows large natural concentration variations, which need to be disentangled from anthropogenic signals to assess changes in associated emissions. This is in principle possible for the fossil fuel CO(2) component (FFCO(2)) by high-precision radiocarbon ((14)C) analyses because FFCO(2) is free of radiocarbon. Long-term observations of (14)CO(2) conducted at two sites in south-western Germany do not yet reveal any significant trends in the regional fossil fuel CO(2) component. We rather observe strong inter-annual variations, which are largely imprinted by changes of atmospheric transport as supported by dedicated transport model simulations of fossil fuel CO(2). In this paper, we show that, depending on the remoteness of the site, changes of about 7-26% in fossil fuel emissions in respective catchment areas could be detected with confidence by high-precision atmospheric (14)CO(2) measurements when comparing 5-year averages if these inter-annual variations were taken into account. This perspective constitutes the urgently needed tool for validation of fossil fuel CO(2) emissions changes in the framework of the Kyoto protocol and successive climate initiatives.

  1. High performance field emission and Nottingham effect observed from carbon nanotube yarn

    Science.gov (United States)

    Choi, Young Chul; Kang, Jun-Tae; Park, Sora; Go, Eunsol; Jeon, Hyojin; Kim, Jae-Woo; Jeong, Jin-Woo; Park, Kyung-Ho; Song, Yoon-Ho

    2017-02-01

    Vertically aligned CNTs were synthesized on a four inch wafer, followed by the preparation of a CNT yarn. The yarn emitter was found to have an extremely high field enhancement factor, which was confirmed to have originated from multi-stage effect. In addition to superb field emission characteristics, the energy exchange during field emission, called Nottingham effect, was observed from the CNT yarn emitter. A CNT yarn was attached to the thermistor whose resistance depends on temperature. Then, the change of resistance was monitored during the field emission, which enabled us to calculate the energy exchange. It was found that the observed heating originated from both Nottingham and Joule heating. Nottingham heating was dominant at low current region while Joule heating became larger contribution at high current region. Very large Nottingham region of up to 33.35 mA was obtained, which is due presumably to the high performance field emission characteristics of a CNT yarn. This is believed to be an important observation for developing reliable field emission devices with suppressed Joule heating effect.

  2. Improved system for perpendicular electron-cyclotron emission measurements on TMX-Upgrade

    Energy Technology Data Exchange (ETDEWEB)

    Lasnier, C.J.; Ellis, R.F.; James, R.A.

    1986-03-07

    Perpendicular electron-cyclotron emission (PECE) is used on TMX-U to diagnose thermal-barrier hot electrons (T/sub H/ approx. 100 to 400 keV); yielding the time history of the temperature of these relativistic electrons. We describe an improved quasi-optical viewing system for these measurements that uses high sensitivity superheterodyne receivers at fixed frequencies of 60, 98, 130, and 196 GHz. The improved viewing and transport system consists of an off-axis ellipsoidal mirror that images the plasma onto a V-band conical collection horn, an overmoded circular waveguide (7/8'' diam) that transports the radiation outside the vacuum vessel where the polarization is selected, and a high absorptivity Macor beam dump to prevent internal wall reflections from entering the viewing system. A relativistic code is used to calculate optically thin PECE signals from relativistic electrons for various energy and pitch angle distributions. 4 refs., 4 figs.

  3. Physics design of the in-vessel collection optics for the ITER electron cyclotron emission diagnostic.

    Science.gov (United States)

    Rowan, W L; Houshmandyar, S; Phillips, P E; Austin, M E; Beno, J H; Hubbard, A E; Khodak, A; Ouroua, A; Taylor, G

    2016-11-01

    Measurement of the electron cyclotron emission (ECE) is one of the primary diagnostics for electron temperature in ITER. In-vessel, in-vacuum, and quasi-optical antennas capture sufficient ECE to achieve large signal to noise with microsecond temporal resolution and high spatial resolution while maintaining polarization fidelity. Two similar systems are required. One views the plasma radially. The other is an oblique view. Both views can be used to measure the electron temperature, while the oblique is also sensitive to non-thermal distortion in the bulk electron distribution. The in-vacuum optics for both systems are subject to degradation as they have a direct view of the ITER plasma and will not be accessible for cleaning or replacement for extended periods. Blackbody radiation sources are provided for in situ calibration.

  4. Direct and Recoil-Induced Electron Emission from Ion-Bombarded Solids

    DEFF Research Database (Denmark)

    Holmen, G.; Svensson, B.; Schou, Jørgen

    1979-01-01

    The kinetic emission of secondary electrons from ion-bombarded solid surfaces is split into two contributions, a direct one caused by ionizing collisions between the bombarding ion and target atoms, and an indirect one originating from ionizing collisions undergone by recoil atoms with other target...... atoms. The direct contribution, which has been treated by several authors in previous studies, shows a behavior that is determined primarily by the electronic stopping power of the bombarding ion, while the indirect contribution is nonproportionally related to the nuclear stopping power. This latter...... contribution is known to be quite important for heavy-ion bombardment at keV energies, and is shown to be of crucial importance for the understanding of the energy dependence of the electron yield in such cases. The model is shown to give consistent results for copper bombarded with electrons, protons...

  5. Adaptive-array Electron Cyclotron Emission diagnostics using data streaming in a Software Defined Radio system

    Science.gov (United States)

    Idei, H.; Mishra, K.; Yamamoto, M. K.; Hamasaki, M.; Fujisawa, A.; Nagashima, Y.; Hayashi, Y.; Onchi, T.; Hanada, K.; Zushi, H.; the QUEST Team

    2016-04-01

    Measurement of the Electron Cyclotron Emission (ECE) spectrum is one of the most popular electron temperature diagnostics in nuclear fusion plasma research. A 2-dimensional ECE imaging system was developed with an adaptive-array approach. A radio-frequency (RF) heterodyne detection system with Software Defined Radio (SDR) devices and a phased-array receiver antenna was used to measure the phase and amplitude of the ECE wave. The SDR heterodyne system could continuously measure the phase and amplitude with sufficient accuracy and time resolution while the previous digitizer system could only acquire data at specific times. Robust streaming phase measurements for adaptive-arrayed continuous ECE diagnostics were demonstrated using Fast Fourier Transform (FFT) analysis with the SDR system. The emission field pattern was reconstructed using adaptive-array analysis. The reconstructed profiles were discussed using profiles calculated from coherent single-frequency radiation from the phase array antenna.

  6. Detailed modeling of electron emission for transpiration cooling of hypersonic vehicles

    Science.gov (United States)

    Hanquist, Kyle M.; Hara, Kentaro; Boyd, Iain D.

    2017-02-01

    Electron transpiration cooling (ETC) is a recently proposed approach to manage the high heating loads experienced at the sharp leading edges of hypersonic vehicles. Computational fluid dynamics (CFD) can be used to investigate the feasibility of ETC in a hypersonic environment. A modeling approach is presented for ETC, which includes developing the boundary conditions for electron emission from the surface, accounting for the space-charge limit effects of the near-wall plasma sheath. The space-charge limit models are assessed using 1D direct-kinetic plasma sheath simulations, taking into account the thermionically emitted electrons from the surface. The simulations agree well with the space-charge limit theory proposed by Takamura et al. for emitted electrons with a finite temperature, especially at low values of wall bias, which validates the use of the theoretical model for the hypersonic CFD code. The CFD code with the analytical sheath models is then used for a test case typical of a leading edge radius in a hypersonic flight environment. The CFD results show that ETC can lower the surface temperature of sharp leading edges of hypersonic vehicles, especially at higher velocities, due to the increase in ionized species enabling higher electron heat extraction from the surface. The CFD results also show that space-charge limit effects can limit the ETC reduction of surface temperatures, in comparison to thermionic emission assuming no effects of the electric field within the sheath.

  7. On Secondary Electron Emission from Solid H2 and D2

    DEFF Research Database (Denmark)

    Schou, Jørgen; Sørensen, H.

    1978-01-01

    The emission of secondary electrons from solid hydrogen (H2 , D2, T2) is often considered to be of importance for the interaction between a fusion plasma and pellets of solid hydrogens. A set-up was therefore built for studies of interactions between energetic particles and solid hydrogens. Studies...... of secondary electron emission (SEE) from solid H2 and D2 were made for incidence of electrons up to 3 keV and for incidence of ions of hydrogen, deuterium, and helium up to 10 keV. The measurements were made for normal incidence, and in some cases also for oblique incidence. The SEE coefficients for solid H2...... is always 0.65-0.70 times that for solid D2. This difference is attributed to different losses to vibrational states in H2 and D2 for the low energy electrons. Measurements were also made on solid para-H2 with both electrons and hydrogen ions. There was no difference from the results for normal H2, which...

  8. Mechanisms of dust grain charging in plasma with allowance for electron emission processes

    Energy Technology Data Exchange (ETDEWEB)

    Mol’kov, S. I.; Savin, V. N., E-mail: moped@onego.ru [Petrozavodsk State University (Russian Federation)

    2017-02-15

    The process of dust grain charging is described with allowance for secondary, ion-induced, photoelectric, and thermal electron emission from the grain surface. The roughness of the grain surface is taken into account. An intermediate charging regime involving ion–atom collisions and electron ionization in the perturbed plasma region is analyzed using the moment equations and Poisson’s equation. A calculation method is proposed that allows one to take into account the influence of all the above effects and determine the radius of the plasma region perturbed by the dust grain.

  9. Imaging the atomic orbitals of carbon atomic chains with field-emission electron microscopy

    Science.gov (United States)

    Mikhailovskij, I. M.; Sadanov, E. V.; Mazilova, T. I.; Ksenofontov, V. A.; Velicodnaja, O. A.

    2009-10-01

    A recently developed high-field technique of atomic chains preparation has made it possible to attain the ultrahigh resolution of field-emission electron microscopy (FEEM), which can be used to direct imaging the intra-atomic electronic structure. By applying cryogenic FEEM, we are able to resolve the spatial configuration of atomic orbitals, which correspond to quantized states of the end atom in free-standing carbon atomic chains. Knowledge of the intra-atomic structure will make it possible to visualize generic aspects of quantum mechanics and also lead to approaches for a wide range of nanotechnological applications.

  10. Mechanisms of dust grain charging in plasma with allowance for electron emission processes

    Science.gov (United States)

    Mol'kov, S. I.; Savin, V. N.

    2017-02-01

    The process of dust grain charging is described with allowance for secondary, ion-induced, photoelectric, and thermal electron emission from the grain surface. The roughness of the grain surface is taken into account. An intermediate charging regime involving ion-atom collisions and electron ionization in the perturbed plasma region is analyzed using the moment equations and Poisson's equation. A calculation method is proposed that allows one to take into account the influence of all the above effects and determine the radius of the plasma region perturbed by the dust grain.

  11. Evidence for moving features in the corona from emission line profiles observed during eclipses

    Science.gov (United States)

    Delone, A. B.; Makarova, E. A.; Iakunina, G. V.

    1988-03-01

    Using the line profiles of forbidden Fe x 6374 A and Fe XIV 5303 A emission lines observed during five total solar eclipses, the problem whether the solar corona is static or contains moving features is addressed. Many of the profiles of both emission lines have complicated shapes, which is interpreted as an evidence for the existence of many, small, moving features in the corona. The line-of-sight velocities observed by other investigators such as Desai et al., 1982 also supported this view. On the other hand, about 15 recent interferometric and multislit investigations of coronal emission lines have not shown evidence of moving elements. It is suggested that this is due to insufficient spatial resolution.

  12. Explosive Emission and Gap Closure from a Relativistic Electron Beam Diode

    Science.gov (United States)

    2013-06-01

    perforated anode for high power microwave (HPM) production or flash X-ray radiography . In accelerator applications, the electrons from cold cathodes are...Bremsstrahlung radiation [3-8]. It is imperative to study the beam physics even in the accelerators used for radiography in order to optimize the...then slowing to 10 cm/ µs. Explosive emission cold cathodes are also employed in virtual cathode oscillators for HPM production [11]. The RITS-6

  13. Temporal Dynamics and Electronic Nose Detection of Stink Bug-Induced Volatile Emissions from Cotton Bolls

    OpenAIRE

    Degenhardt, David C.; Greene, Jeremy K.; Ahmad Khalilian

    2012-01-01

    Management decisions for stink bugs (Pentatomidae) in Bt cotton are complicated by time-consuming sampling methods, and there is a need for more efficient detection tools. Volatile compounds are released from cotton bolls in response to feeding by stink bugs, and electronic nose (E-nose) technology may be useful for detecting boll damage. In this study, we investigated the temporal dynamics of volatile emissions in response to feeding by stink bugs and tested the ability of E-nose to discrimi...

  14. Ultrasoft X-ray emission and the electronic structure of the acetaldehyde molecule

    Science.gov (United States)

    Davydova, N. V.; Yumatov, V. D.

    2012-07-01

    The electronic structure of the acetaldehyde molecule was studied by the ultrasoft X-ray emission method with the use of quantum-chemical calculations. The O K α and C K α spectra of the compound in the gas phase were obtained. Quantum-chemical calculations were performed at the RHF/6-311++G** level. The calculation results were used to construct theoretical X-ray spectra. The experimental spectra are interpreted.

  15. The Nanophysics of Electron Emission and Breakdown for High Power Microwave Source

    Science.gov (United States)

    2009-12-21

    coaxial anode/collector. 3.1.2. Formation of  plasma  filaments during w‐band microwave breakdown  Regular, two-dimensional plasma ...Injection Gun ," IEEE Trans. Elec. Devices (May, 2005). 2. Booske, John H., “ Plasma physics and related challenges of millimeter-to-terahertz and...high power microwave (HPM) device technologies by establishing new physical understanding of electron emission/absorption and plasma breakdown

  16. Statistical simulation of the energy spectra of field-emission electrons

    Science.gov (United States)

    Egorov, N. V.; Antonov, A. Yu.; Demchenko, N. S.

    2017-02-01

    Random energies of electrons that escape from the source in the course of field emission are simulated using energy spectra. A relationship of the random values of total energy and the energy related to the normal (with respect to surface) component of momentum is established. A family of quadrature formulas needed for the integration of the distribution density of particles is analyzed. A hypothesis on the compliance of selected random energies with desired distribution laws is statistically tested.

  17. Observation of whispering gallery modes through electron beam-induced deposition

    NARCIS (Netherlands)

    Timmermans, F. J.; Chang, L.; Van Wolferen, H. A.G.M.; Lenferink, A. T.M.; Otto, C.

    2017-01-01

    Surprisingly intense spectra of whispering gallery modes were observed in polymer microbeads after illumination with electrons in a scanning electron microscope and subsequent laser illumination and spectral analysis. It will be proposed that whispering gallery mode resonances became visible after

  18. Relativistic attosecond electron bunch emission from few-cycle laser irradiated nanoscale droplets

    Directory of Open Access Journals (Sweden)

    Laura Di Lucchio

    2015-02-01

    Full Text Available Attosecond electron bunches produced at the surface of nanometer-scale droplets illuminated by a two-cycle laser pulse are investigated for the purpose of determining their optimal emission characteristics. Significant departures from Mie theory are found for electron bunch emission from droplets whose radii satisfy the condition δ_{r}emission of the bunches is to a good approximation described by the nonlinear ponderomotive scattering model. Subsequently, the bunches are subject to further deflection by the ponderomotive pressure of the copropagating laser field in vacuum, depending on the initial droplet parameters. Final emission angles are estimated, together with the energy spectrum of the bunches.

  19. Constraining atmospheric ammonia emissions through new observations with an open-path, laser-based sensor

    Science.gov (United States)

    Sun, Kang

    As the third most abundant nitrogen species in the atmosphere, ammonia (NH3) is a key component of the global nitrogen cycle. Since the industrial revolution, humans have more than doubled the emissions of NH3 to the atmosphere by industrial nitrogen fixation, revolutionizing agricultural practices, and burning fossil fuels. NH3 is a major precursor to fine particulate matter (PM2.5), which has adverse impacts on air quality and human health. The direct and indirect aerosol radiative forcings currently constitute the largest uncertainties for future climate change predictions. Gas and particle phase NH3 eventually deposits back to the Earth's surface as reactive nitrogen, leading to the exceedance of ecosystem critical loads and perturbation of ecosystem productivity. Large uncertainties still remain in estimating the magnitude and spatiotemporal patterns of NH3 emissions from all sources and over a range of scales. These uncertainties in emissions also propagate to the deposition of reactive nitrogen. To improve our understanding of NH3 emissions, observational constraints are needed from local to global scales. The first part of this thesis is to provide quality-controlled, reliable NH3 measurements in the field using an open-path, quantum cascade laser-based NH3 sensor. As the second and third part of my research, NH3 emissions were quantified from a cattle feedlot using eddy covariance (EC) flux measurements, and the similarities between NH3 turbulent fluxes and those of other scalars (temperature, water vapor, and CO2) were investigated. The fourth part involves applying a mobile laboratory equipped with the open-path NH3 sensor and other important chemical/meteorological measurements to quantify fleet-integrated NH3 emissions from on-road vehicles. In the fifth part, the on-road measurements were extended to multiple major urban areas in both the US and China in the context of five observation campaigns. The results significantly improved current urban NH3

  20. Coherent electron emission for dissociative ionization of molecular hydrogen by electron impact

    Energy Technology Data Exchange (ETDEWEB)

    Fojon, O A; Stia, C R; Rivarola, R D, E-mail: ofojon@fceia.unr.edu.ar [Instituto de Fisica Rosario, CONICET and Universidad Nacional de Rosario, Av. Pellegrini 250, 2000 Rosario (Argentina)

    2011-04-01

    The single ionization of hydrogen molecules is studied theoretically as a function of the molecular alignment. Within the framework of the two-effective center model, multiple differential cross sections as a function of both electron momenta in the final channel of the reaction, and the internuclear orientation, are computed for both non-dissociative and dissociative final H{sup +}{sub 2} states. Preliminary results show that the interference pattern arising from the two-center character of the molecular target changes strongly with the final state of the residual molecular ion.

  1. Experimental Observation of Direct Particle Acceleration by Stimulated Emission of Radiation

    Science.gov (United States)

    Banna, Samer; Berezovsky, Valery; Schächter, Levi

    2006-09-01

    We report the first experimental evidence for direct particle acceleration by stimulated emission of radiation. In the framework of this proof-of-principle experiment, a 45 MeV electron macrobunch was modulated by a high-power CO2 laser and then injected into an excited CO2 gas mixture. The emerging microbunches experienced a 0.15% relative change in the kinetic energy, in a less than 40 cm long interaction region. According to our experimental results, a fraction of these electrons have gained more than 200 keV each, implying that such an electron has undergone an order of magnitude of 2×106 collisions of the second kind.

  2. Electron field emission from freestanding Diamond nanomembranes and Application to time-of-flight mass spectrometry

    Science.gov (United States)

    Kim, Hyunseok; Park, Jonghoo; Shin, Hyuncheol; Blick, Robert H.

    2013-03-01

    We introduce a prototype of a freestanding diamond nanomembrane for large protein detection in time-of-flight mass spectrometry. Doped diamond as a material for mass spectroscopy is extremely interesting due to its mechanical and electrical properties. The freestanding diamond nanomembranes we are able to fabricate have lateral extensions of 400 μm × 400 μm with a thickness of 100nm. We employ optical lithography and a Buffered Oxide Etch (BOE) of SiO2 followed by anisotropic etching of the substrate silicon using TMAH solution and finally removing SiO2. The electron field emission from the surface of the membrane is traced in the IV characteristics at room temperature. The membrane is then applied for detection of the large ionized proteins using time-of-flight mass spectrometry. Ion detection is demonstrated in our nanomembrane MALDI-TOF analysis of Insulin (5,735 Da). That is when the ions with a large kinetic energy bombard the nanomembrane, their energy is thermalized upon impact into phonons. The phonons give a thermal energy to the electrons with the membrane, which are then excited to higher energetic states. Given an extraction voltage this leads to electron field emission from the membrane which we labeled phonon-assisted field emission (PAFE). In other words, the MALDI mass spectra are obtained by exploiting ballistic phonon propagation and quasi-diffusive phonon propagation.

  3. Secondary Electron Emission From Solar Cell Coverslides And Its Effect On Absolute Vehicle Charging

    Science.gov (United States)

    Ferguson, Dale C.

    2011-10-01

    It has often been stated that earthed conductive solar cell coverslides are the best way to prevent electrostatic discharges on space solar arrays in GEO. While it is true that such coverslides will prevent differential charging on the solar arrays, it will be shown through NASCAP- 2k simulations that the secondary electron emission of such coverslides is very important for absolute vehicle charging. In particular, carbon nanotube coatings, due to the extremely low secondary electron emission from carbon, may exacerbate absolute vehicle charging. However, if they are earthed, because of their conductivity they may minimize differential charging and the possibility of arcing elsewhere on the spacecraft. Such results may also be true for insulative coverslides if spacecraft thermal blankets are made of materials with high secondary electron emission. Finally, photoemission from coverslides is investigated, with regard to anti-reflection coatings. Surfaces which reflect UV can have low photoemission, while those that absorb may have higher photoemission rates. Thus, anti-reflection coatings may lead to higher absolute spacecraft charging rates. NASCAP-2k simulations will be used to investigate these dependences for realistic spacecraft.

  4. Dual Effort to Correlate the Electron Field Emission Performance of Carbon Nanotubes with Synthesis As Well As Annealing Temperature: Theoretical Support of the Experimental Finding.

    Science.gov (United States)

    Maity, Supratim; Banerjee, Diptonil; Das, Nirmalya Sankar; Chattopadhyay, Kalyan Kumar

    2016-05-01

    Here a dual approach has been adopted to study the effect of both synthesis as well as annealing temperature on the electron field emission property of differently synthesized carbon nanotubes (CNTs) that include solid state chemical reaction as well as chemical vapour deposition (CVD). Experimental findings were supported by theoretical simulation. All the samples were characterized by X-ray diffraction (XRD), Fourier transformed infrared spectroscopy, Raman spectroscopy, field emission scanning electron microscopy (FESEM) and transmission electron microscopy (TEM). XRD as well as TEM study confirms the amorphous nature (aCNTs) of the samples for both the synthesis techniques which is attributed to lower synthesis temperature. Prominent morphological differences of these two types of aCNTs are clearly observed from both FESEM and TEM images. It is found that electron field emission characteristics of aCNTs synthesized by CVD shows better field emission properties as compared to aCNTs synthesized by solid state reaction. Finite element based simulation shows that temperature has prominent effect on morphology, screening effect or degree of graphitization that leads to improved field emission characteristics for the CVD synthesized aCNTs.

  5. Effects of Energetic Solar Emissions on the Lower Ionosphere as seen in Ionosonde Observations

    Science.gov (United States)

    Barta, V.; Satori, G.; Williams, E.

    2016-12-01

    The sudden increase of X-radiation and EUV emission following solar flares causes extra ionization in the sunlit hemisphere in the D- and E-regions of the Earth's ionosphere. In addition, solar flares are also accompanied by energetic particles (protons and electrons) with energies from tens of keV to hundreds of MeV result additional ionization. The impact of two exceptional solar events - the Bastille Day event (July 14, 2000) and the Halloween event (Oct/Nov2003) on the lowest region of the ionosphere (European stations (Juliusruh, 53.6°N, 13.4°E; Chilton, 51.5°N, 359.4°E; Rome, 41.9°N, 12.5°E; SanVito 40.6°N, 17.8°E) during the Halloween event. This ionosonde response increases with increasing latitude. Simultaneously the absence of the foE parameter was observed. The sharply increased values (2-4 MHz) of the fmin parameters and the co-occurring absence of the foE parameters were detected in the case of the Bastille Day event as well, but only at high latitude stations (Loparskaya, 68°N, 33°E; St. Petersburg, 59.9°N, 30.3°E; Juliusruh, 53.6°N, 13.4°E). These results suggest that the latitude-dependent change of the fmin and foE parameters is related to energetic solar particles penetrating to the lower ionosphere.

  6. Short-term observations of double-peaked Na emission from Mercury's exosphere

    Science.gov (United States)

    Massetti, S.; Mangano, V.; Milillo, A.; Mura, A.; Orsini, S.; Plainaki, C.

    2017-04-01

    We report the analysis of short-term ground-based observations of the exospheric Na emission (D1 and D2 lines) from Mercury, which was characterized by two high-latitude peaks confined near the magnetospheric cusp footprints. During a series of scheduled observations from the Télescope Héliographique pour l'Etude du Magnétisme et des Instabilités Solaires (THEMIS) telescope, achieved by scanning the whole planet, we implemented a series of extra measurements by recording the Na emission from a narrow north-south strip only, centered above the two emission peaks. Our aim was to inspect the existence of short-term variations, which were never analyzed before from ground-based observations, and their possible correlation with interplanetary magnetic field variations. Though Mercury possesses a miniature magnetosphere, characterized by fast reconnection events that develop on a timescale of few minutes, ground-based observations show that the exospheric Na emission pattern can be globally stable for a prolonged period (some days) and also exhibits fluctuations in the time range of tens of minutes.

  7. Simultaneous NIR/sub-mm observation of flare emission from Sagittarius A*

    NARCIS (Netherlands)

    Eckart, A.; Schödel, R.; García-Marín, M.; Witzel, G.; Weiss, A.; Baganoff, F.K.; Morris, M.R.; Bertram, T.; Dovčiak, M.; Duschl, W.J.; Karas, V.; König, S.; Krichbaum, T.P.; Krips, M.; Kunneriath, D.; Lu, R.-S.; Markoff, S.; Mauerhan, J.; Meyer, L.; Moultaka, J.; Mužić, K.; Najarro, F.; Pott, J.-U.; Schuster, K.F.; Sjouwerman, L.O.; Straubmeier, C.; Thum, C.; Vogel, S.N.; Wiesemeyer, H.; Zamaninasab, M.; Zensus, J.A.

    2008-01-01

    Context. We report on a successful, simultaneous observation and modeling of the sub-millimeter to near-infrared flare emission of the Sgr A* counterpart associated with the super-massive (4 x 10(6) M-circle dot) black hole at the Galactic center. Aims. We study and model the physical processes

  8. Radio and γ-ray emissions from pulsars: possible observational tests

    Science.gov (United States)

    Qiao, G. J.; Lee, K. J.; Wang, H. G.; Xu, R. X.; Zhang, B.

    2008-01-01

    Many models for the pulsar radio and γ-ray emissions have been developed. The tests for these models using observational data are very important. Tests for the pulsar radio emission models using frequency-altitude relation are presented in this paper. In the radio band, the mean pulse profiles evolve with observing frequencies. There are various styles of pulsar profile-frequency evolutions (which we call as ``beam evolution'' figure), e.g. some pulsars show that mean pulse profiles are wider and core emission is higher at higher frequencies than that at lower frequencies, but some other pulsars show completely the contrary results. We show that all these ``beam evolution'' figures can be understood by the Inverse Compton Scattering (ICS) model (see Qiao et al. 2001 also). An important observing test is that, for a certain observing frequency different emission components are radiated from the different heights. For the γ-ray pulsars, the geometrical method (Wang et al. 2006) can be used to diagnose the radiation location for the γ-ray radiation. As an example, Wang et al. (2006) constrain the γ-ray radiation location of PSR B1055-52 to be the place near the null charge surface. Here we show that Wang's result matches the proposed radiation locations by the annular gap model as well as the outer gap models.

  9. Unusually high frequency natural VLF radio emissions observed during daytime in Northern Finland

    Science.gov (United States)

    Manninen, Jyrki; Turunen, Tauno; Kleimenova, Natalia; Rycroft, Michael; Gromova, Liudmila; Sirviö, Iina

    2016-12-01

    Geomagnetic field variations and electromagnetic waves of different frequencies are ever present in the Earth’s environment in which the Earth’s fauna and flora have evolved and live. These waves are a very useful tool for studying and exploring the physics of plasma processes occurring in the magnetosphere and ionosphere. Here we present ground-based observations of natural electromagnetic emissions of magnetospheric origin at very low frequency (VLF, 3-30 kHz), which are neither heard nor seen in their spectrograms because they are hidden by strong impulsive signals (sferics) originating in lightning discharges. After filtering out the sferics, peculiar emissions are revealed in these digital recordings, made in Northern Finland, at unusually high frequencies in the VLF band. These recently revealed emissions, which are observed for several hours almost every day in winter, contain short (˜1-3 min) burst-like structures at frequencies above 4-6 kHz, even up to 15 kHz; fine structure on the 1 s time scale is also prevalent. It seems that these whistler mode emissions are generated deep inside the magnetosphere, but the detailed nature, generation region and propagation behaviour of these newly discovered high latitude VLF emissions remain unknown; however, further research on them may shed new light on wave-particle interactions occurring in the Earth’s radiation belts.

  10. Using Lunar Observations to Assess Terra MODIS Thermal Emissive Bands Calibration

    Science.gov (United States)

    Xiong, Xiaoxiong; Chen, Hongda

    2010-01-01

    MODIS collects data in both the reflected solar and thermal emissive regions using 36 spectral bands. The center wavelengths of these bands cover the3.7 to 14.24 micron region. In addition to using its on-board calibrators (OBC), which include a full aperture solar diffuser (SD) and a blackbody (BB), lunar observations have been scheduled on a regular basis to support both Terra and Aqua MODIS on-orbit calibration and characterization. This paper provides an overview of MODIS lunar observations and their applications for the reflective solar bands (RSB) and thermal emissive bands (TEB) with an emphasis on potential calibration improvements of MODIS band 21 at 3.96 microns. This spectral band has detectors set with low gains to enable fire detection. Methodologies are proposed and examined on the use of lunar observations for the band 21 calibration. Also presented in this paper are preliminary results derived from Terra MODIS lunar observations and remaining challenging issues.

  11. Quantum well state of cubic inclusions in hexagonal silicon carbide studied with ballistic electron emission microscopy

    Science.gov (United States)

    Ding, Yi

    SiC is a polytypic material that may crystallize in many different close-packing sequences with cubic, hexagonal, or rhombohedral Bravais lattices. All SiC polytypes have wide bandgaps ranging from 2.39 eV in cubic SiC to 3.023--3.330 eV in common hexagonal polytypes. This, as well as many other properties favorable to electrical applications, makes SiC a very promising material in electronic device fabrication. However, the many lattice stacking sequences may impair the stability of SiC devices. In the hexagonal 4H polytype, it has been found that thin cubic SiC inclusions may be formed due to stacking fault expansion, and it has been proposed that the inclusions may behave as quantum wells because of the lower bandgap of cubic SiC. We performed ultra-high vacuum ballistic electron emission microscopy (BEEM) measurements on n-type 4H-SiC samples containing double-stacking-fault cubic inclusions to characterize the electrical properties of individual inclusions. Thin Pt films are deposited in ultra-high vacuum on the sample surfaces to form Schottky contacts. A Schottky barrier height of ˜1.01 eV is observed over the inclusions in a background of normal 4H-SiC barrier height of 1.54 eV, which directly confirms the cubic inclusions support two-dimensional propagating quantum well states, and the 0.53 eV lowering of barrier height indicates the two-dimensional conduction band minimum is located at ˜0.53 eV below the conduction band minimum of bulk 4H-SIC. We also used BEEM to study the Schottky contact between Pt and p-type 4H-SiC, and observed a second transmission channel in the BEEM spectrum that suggests a split-off valence band at ˜0.11 eV below the valence band maximum. We also measured the barrier heights of p-type and n-type Schottky contacts prepared under identical conditions and the results suggest the existence of an interfacial layer. An earlier study of threading dislocations in GaN using BEEM is also described. Although threading dislocations in Ga

  12. Calibration and use cases of the electron cyclotron emission diagnostic at Wendelstein 7-X

    Energy Technology Data Exchange (ETDEWEB)

    Hoefel, Udo; Hirsch, Matthias; Ewert, Karsten; Hartfuss, Hans-Juergen; Laqua, Heinrich Peter; Stange, Torsten; Wolf, Robert [Max-Planck-Institut fuer Plasmaphysik, Greifswald (Germany); Collaboration: the W7-X Team

    2016-07-01

    The world's largest stellarator, Wendelstein 7-X (W7-X), is equipped with a 140 GHz electron cyclotron resonance heating (ECRH) system providing up to 5 MW absorbed power in the first operation phase OP1.1. The foreseen X2-heating scenario uses the high absorption of the second harmonic extraordinary electron cyclotron waves, which leads on the other hand to a black body electron cyclotron emission (ECE) being proportional to the local electron temperature. ECE is one of the fundamental operating diagnostics and is planned to yield the electron temperature profile from the very first discharges onwards. Unlike most other ECE diagnostics, the 32 channel ECE radiometer diagnostic (with additional 16 channels with higher radial resolution) at W7-X is absolutely calibrated. It is planned to use this diagnostic for intensive studies on electron heat transport in the upcoming operational phases of W7-X. Simple switch-off experiments for the determination of the energy confinement time should already be possible within the first plasma shots. Due to the high temporal and radial resolution the ECE will be used also to determine the power deposition by modulation of the heating gyrotron. or the localization of a power modulated ECRH to optimize the power deposition. If reasonably equilibrated plasma conditions could be generated in the first operational phase (OP 1.1), first studies on electron thermal diffusivity could also be possible.

  13. Particulate Matter from Electronic Cigarettes and Conventional Cigarettes: a Systematic Review and Observational Study.

    Science.gov (United States)

    Fernández, Esteve; Ballbè, Montse; Sureda, Xisca; Fu, Marcela; Saltó, Esteve; Martínez-Sánchez, Jose M

    2015-12-01

    The aim of this study is to review the literature on the composition of aerosols from electronic cigarettes (e-cigarettes) originated by human vaping and to describe the emission of particulate matter ≤ 2.5 μm in diameter (PM(2.5)) from conventional and e-cigarettes at home in real-use conditions. We conducted a systematic literature search in PubMed and Web of Science. We measured PM(2.5) in four different homes: one from a conventional cigarette smoker, one from an e-cigarette user, and two from non-smokers. The review identified eight previous investigations on the composition of aerosols from e-cigarettes originated by human vaping and indicated that emissions from e-cigarettes can contain potential toxic compounds such as nicotine, carbonyls, metals, and organic volatile compounds, besides particulate matter. In the observational study, the PM(2.5) median concentration was 9.88 μg/m³ in the e-cigarette user home and 9.53 and 9.36 μg/m³ in the smoke-free homes, with PM(2.5) peaks concurrent with the e-cigarette puffs. Both the literature review and the observational study indicate that e-cigarettes used under real-conditions emit toxicants, including PM(2.5). Further research is needed to characterize the chemicals emitted by different types of e-cigarettes and to assess secondhand exposure to e-cigarette aerosol using biological markers.

  14. Field-emission scanning electron microscopy of the internal cellular organization of fungi

    NARCIS (Netherlands)

    Muller, W.H.; Aelst, van A.C.; Humbel, B.M.; Krift, van der T.P.; Boekhout, T.

    2000-01-01

    Internal viewing of the cellular organization of hyphae by scanning electron microscopy is an alternative to observing sectioned fungal material with a transmission electron microscope. To study cytoplasmic organelles in the hyphal cells of fungi by SEM, colonies were chemically fixed with

  15. Emissions from Electronic Cigarettes: Key Parameters Affecting the Release of Harmful Chemicals.

    Science.gov (United States)

    Sleiman, Mohamad; Logue, Jennifer M; Montesinos, V Nahuel; Russell, Marion L; Litter, Marta I; Gundel, Lara A; Destaillats, Hugo

    2016-09-06

    Use of electronic cigarettes has grown exponentially over the past few years, raising concerns about harmful emissions. This study quantified potentially toxic compounds in the vapor and identified key parameters affecting emissions. Six principal constituents in three different refill "e-liquids" were propylene glycol (PG), glycerin, nicotine, ethanol, acetol, and propylene oxide. The latter, with mass concentrations of 0.4-0.6%, is a possible carcinogen and respiratory irritant. Aerosols generated with vaporizers contained up to 31 compounds, including nicotine, nicotyrine, formaldehyde, acetaldehyde, glycidol, acrolein, acetol, and diacetyl. Glycidol is a probable carcinogen not previously identified in the vapor, and acrolein is a powerful irritant. Emission rates ranged from tens to thousands of nanograms of toxicants per milligram of e-liquid vaporized, and they were significantly higher for a single-coil vs a double-coil vaporizer (by up to an order of magnitude for aldehydes). By increasing the voltage applied to a single-coil device from 3.3 to 4.8 V, the mass of e-liquid consumed doubled from 3.7 to 7.5 mg puff(-1) and the total aldehyde emission rates tripled from 53 to 165 μg puff(-1), with acrolein rates growing by a factor of 10. Aldehyde emissions increased by more than 60% after the device was reused several times, likely due to the buildup of polymerization byproducts that degraded upon heating. These findings suggest that thermal degradation byproducts are formed during vapor generation. Glycidol and acrolein were primarily produced by glycerin degradation. Acetol and 2-propen-1-ol were produced mostly from PG, while other compounds (e.g., formaldehyde) originated from both. Because emissions originate from reaction of the most common e-liquid constituents (solvents), harmful emissions are expected to be ubiquitous when e-cigarette vapor is present.

  16. Transcribing RNA polymerase III observed by electron cryomicroscopy.

    Science.gov (United States)

    Hoffmann, Niklas A; Jakobi, Arjen J; Vorländer, Matthias K; Sachse, Carsten; Müller, Christoph W

    2016-08-01

    Electron cryomicroscopy reconstructions of elongating RNA polymerase (Pol) III at 3.9 Å resolution and of unbound Pol III (apo Pol III) in two distinct conformations at 4.6 Å and 4.7 Å resolution allow the construction of complete atomic models of Pol III and provide new functional insights into the adaption of Pol III to fulfill its specific transcription tasks. © 2016 The Authors. The FEBS Journal published by John Wiley & Sons Ltd on behalf of Federation of European Biochemical Societies.

  17. Ion Gyro-Harmonic Structuring in the Stimulated Electromagnetic Emission Spectrum During Second Electron Gyro-Harmonic Heating

    Science.gov (United States)

    Scales, Wayne; Bernhardt, Paul; Samimi, Alireza; Bricinsky, Stanley; Selcher, Craig

    2012-07-01

    Recent observations of Stimulated Electromagnetic Emissions SEEs have shown structures ordered by the ion gyro-frequency. In particular, during experiments in which the heating frequency is near the second electron gyro-harmonic, unique discrete spectral features separated by the ion gyro-frequency have been observed within about 1 kHz of the pump frequency. On occasion, a broadband spectral feature near 500 Hz is observed that coexists with the ion gyro-harmonic spectral features. Explanations for these spectral features have been based on parametric decay of the pump field into upper hybrid/electron Bernstein and ion Bernstein and oblique ion acoustic waves at the upper hybrid layer. This presentation will first review important characteristics of these ion gyro-harmonic spectral features obtained during some recent experiments at the High Frequency Active Auroral Research HAARP facility. These characteristics are then compared to predications of an analytical model for three-wave parametric decay of the pump field into upper hybrid/electron Bernstein and ion Bernstein and oblique ion acoustic waves. It is shown from the analytical theory that important pump field parameters that influence the spectral characteristics include the angle of the pump field relative the background magnetic field, the frequency of the pump relative to the second gyro-harmonic, and the pump field strength. Two Dimensional Particle-In-Cell simulations are used to investigate aspects of the nonlinear evolution such as irregularity development and field aligned electron heating in more detail. These simulations show favorable comparisons with the analytical theory predications as well as the experimental observations. Finally, possibilities for utilizing the experimentally observed SEE spectra for diagnostic purposes are discussed.

  18. STEM imaging of 47-pm-separated atomic columns by a spherical aberration-corrected electron microscope with a 300-kV cold field emission gun.

    Science.gov (United States)

    Sawada, Hidetaka; Tanishiro, Yasumasa; Ohashi, Nobuhiro; Tomita, Takeshi; Hosokawa, Fumio; Kaneyama, Toshikatsu; Kondo, Yukihito; Takayanagi, Kunio

    2009-12-01

    A spherical aberration-corrected electron microscope has been developed recently, which is equipped with a 300-kV cold field emission gun and an objective lens of a small chromatic aberration coefficient. A dumbbell image of 47 pm spacing, corresponding to a pair of atomic columns of germanium aligned along the [114] direction, is resolved in high-angle annular dark field (HAADF) scanning transmission electron microscopy (STEM) with a 0.4-eV energy spread of the electron beam. The observed image was compared with a simulated image obtained by dynamical calculation.

  19. Synthesis of carbon nanofibres from waste chicken fat for field electron emission applications

    Energy Technology Data Exchange (ETDEWEB)

    Suriani, A.B., E-mail: absuriani@yahoo.com [Nanotechnology Research Centre, Faculty of Science and Mathematics, Universiti Pendidikan Sultan Idris, Tanjung Malim, Perak 35900 (Malaysia); Department of Physics, Faculty of Science and Mathematics, Universiti Pendidikan Sultan Idris, Tanjung Malim, Perak 35900 (Malaysia); Dalila, A.R. [Nanotechnology Research Centre, Faculty of Science and Mathematics, Universiti Pendidikan Sultan Idris, Tanjung Malim, Perak 35900 (Malaysia); Department of Physics, Faculty of Science and Mathematics, Universiti Pendidikan Sultan Idris, Tanjung Malim, Perak 35900 (Malaysia); Mohamed, A.; Isa, I.M.; Kamari, A.; Hashim, N. [Nanotechnology Research Centre, Faculty of Science and Mathematics, Universiti Pendidikan Sultan Idris, Tanjung Malim, Perak 35900 (Malaysia); Department of Chemistry, Faculty of Science and Mathematics, Universiti Pendidikan Sultan Idris, Tanjung Malim, Perak 35900 (Malaysia); Soga, T.; Tanemura, M. [Department of Frontier Materials, Nagoya Institute of Technology, Gokiso-cho, Showa-ku, Nagoya 466-8555 (Japan)

    2015-10-15

    Highlights: • Waste chicken fat is used as a starting material to produce CNFs via TCVD method. • High heating rate applied resulted in aggregation of catalyst particles. • Aggregated catalyst produced sea urchin-like CNFs with amorphous nature. • The as-grown CNFs presented a potential for field electron emission applications. - Abstract: Carbon nanofibres (CNFs) with sea urchin-like morphology were synthesised from waste chicken fat precursor via catalytic thermal chemical vapour deposition method at 750 °C. The CNFs showed amorphous structures under high-resolution transmission electron microscopy, micro-Raman spectroscopy and X-ray diffraction examination. X-ray photoelectron spectroscopy analysis confirmed that the core of the sea urchin-like CNFs was composed of Fe{sub 3}C formed within the first 20 min of synthesis time. The growth of amorphous CNFs from agglomerated Fe{sub 3}C particles was favourable due to the high heating rate applied during the synthesis. Field electron emission examination of the CNFs indicated turn-on and threshold field values of 5.4 and 6.6 V μm{sup −1} at current density of 1 and 10 μA cm{sup −2}, respectively. This study demonstrates that waste chicken fat, a low-cost and readily available resource, can be used as an inexpensive carbon source for the production of CNFs with a potential application in field electron emitters.

  20. Ultraviolet and Extreme-Ultraviolet Emissions at the Flare Footpoints Observed by Atmosphere Imaging Assembly

    Science.gov (United States)

    Qiu, Jiong; Sturrock, Zoe; Longcope, Dana W.; Klimchuk, James A.; Liu, Wen-Juan

    2013-01-01

    A solar flare is composed of impulsive energy release events by magnetic reconnection, which forms and heats flare loops. Recent studies have revealed a two-phase evolution pattern of UV 1600 A emission at the feet of these loops: a rapid pulse lasting for a few seconds to a few minutes, followed by a gradual decay on timescales of a few tens of minutes. Multiple band EUV observations by the Atmosphere Imaging Assembly further reveal very similar signatures. These two phases represent different but related signatures of an impulsive energy release in the corona. The rapid pulse is an immediate response of the lower atmosphere to an intense thermal conduction flux resulting from the sudden heating of the corona to high temperatures (we rule out energetic particles due to a lack of significant hard X-ray emission). The gradual phase is associated with the cooling of hot plasma that has been evaporated into the corona. The observed footpoint emission is again powered by thermal conduction (and enthalpy), but now during a period when approximate steady-state conditions are established in the loop. UV and EUV light curves of individual pixels may therefore be separated into contributions from two distinct physical mechanisms to shed light on the nature of energy transport in a flare.We demonstrate this technique using coordinated, spatially resolved observations of UV and EUV emissions from the footpoints of a C3.2 thermal flare.

  1. Electron emission from conductors subjected to intense, short-pulse electric fields

    Science.gov (United States)

    Scarpetti, R. D.; Goerz, D. A.; Bowen, P. R.; Hodgin, R. L.; Wong, K. C.; Champney, P. D'a.

    1987-06-01

    We studied electron emission from metal electrodes subjected to electric fields ranging from 0.5 to 2.5 MV/cm for pulse durations of 3 to 10 ns. We used two high-voltage pulsers for these tests; a 500 to 700 kV, 72 ohm pulser that generated a 3 ns Gaussian pulse; and a 2 MV, 60 ohm pulser that generated a 10 ns flat-top pulse with a 1-ns risetime. The high voltage levels allowed emission studies using electrode spacings of several millimeters to several centimeters. Our studies emphasized bare and anodized aluminum surface shaving surface finishes that ranged from rolled stock to machined finishes of 2 to 400 micron-in roughness. We also investigated polished stainless steel and brass. Emphasis was on first-shot performance with subsequent pulses applied to check for possible conditioning. The background pressure was typically .00005 Torr. Our studies showed that for 10 ns pulse lengths, anodized aluminum surfaces could hold off more than twice the electric field strength of bare aluminum surfaces without appreciable electron emission. Anodized surfaces performed well at 1.0 to 1.5 MV/cm, while bare surfaces emitted at 0.5 to 0.7 MV/cm. For the shorter, 3 ns pulse lengths, anodizing was less effective at improving suppression of electron emission, while surface finish became the important factor. Electrodes with surface finishes of 40 micro-in or better roughness performed well at field strengths of up to 2.4 MV/cm. The behavior of velvet cloth as an emitter was also investigated using the 3 ns pulser. We found that velvet would emit within 3 ns at field strengths approaching 100 kV/cm.

  2. Nine years of global hydrocarbon emissions based on source inversion of OMI formaldehyde observations

    Directory of Open Access Journals (Sweden)

    M. Bauwens

    2016-08-01

    Full Text Available As formaldehyde (HCHO is a high-yield product in the oxidation of most volatile organic compounds (VOCs emitted by fires, vegetation, and anthropogenic activities, satellite observations of HCHO are well-suited to inform us on the spatial and temporal variability of the underlying VOC sources. The long record of space-based HCHO column observations from the Ozone Monitoring Instrument (OMI is used to infer emission flux estimates from pyrogenic and biogenic volatile organic compounds (VOCs on the global scale over 2005–2013. This is realized through the method of source inverse modeling, which consists in the optimization of emissions in a chemistry-transport model (CTM in order to minimize the discrepancy between the observed and modeled HCHO columns. The top–down fluxes are derived in the global CTM IMAGESv2 by an iterative minimization algorithm based on the full adjoint of IMAGESv2, starting from a priori emission estimates provided by the newly released GFED4s (Global Fire Emission Database, version 4s inventory for fires, and by the MEGAN-MOHYCAN inventory for isoprene emissions. The top–down fluxes are compared to two independent inventories for fire (GFAS and FINNv1.5 and isoprene emissions (MEGAN-MACC and GUESS-ES. The inversion indicates a moderate decrease (ca. 20 % in the average annual global fire and isoprene emissions, from 2028 Tg C in the a priori to 1653 Tg C for burned biomass, and from 343 to 272 Tg for isoprene fluxes. Those estimates are acknowledged to depend on the accuracy of formaldehyde data, as well as on the assumed fire emission factors and the oxidation mechanisms leading to HCHO production. Strongly decreased top–down fire fluxes (30–50 % are inferred in the peak fire season in Africa and during years with strong a priori fluxes associated with forest fires in Amazonia (in 2005, 2007, and 2010, bushfires in Australia (in 2006 and 2011, and peat burning in Indonesia (in 2006 and 2009, whereas

  3. Nine years of global hydrocarbon emissions based on source inversion of OMI formaldehyde observations

    Science.gov (United States)

    Bauwens, Maite; Stavrakou, Trissevgeni; Müller, Jean-François; De Smedt, Isabelle; Van Roozendael, Michel; van der Werf, Guido R.; Wiedinmyer, Christine; Kaiser, Johannes W.; Sindelarova, Katerina; Guenther, Alex

    2016-08-01

    As formaldehyde (HCHO) is a high-yield product in the oxidation of most volatile organic compounds (VOCs) emitted by fires, vegetation, and anthropogenic activities, satellite observations of HCHO are well-suited to inform us on the spatial and temporal variability of the underlying VOC sources. The long record of space-based HCHO column observations from the Ozone Monitoring Instrument (OMI) is used to infer emission flux estimates from pyrogenic and biogenic volatile organic compounds (VOCs) on the global scale over 2005-2013. This is realized through the method of source inverse modeling, which consists in the optimization of emissions in a chemistry-transport model (CTM) in order to minimize the discrepancy between the observed and modeled HCHO columns. The top-down fluxes are derived in the global CTM IMAGESv2 by an iterative minimization algorithm based on the full adjoint of IMAGESv2, starting from a priori emission estimates provided by the newly released GFED4s (Global Fire Emission Database, version 4s) inventory for fires, and by the MEGAN-MOHYCAN inventory for isoprene emissions. The top-down fluxes are compared to two independent inventories for fire (GFAS and FINNv1.5) and isoprene emissions (MEGAN-MACC and GUESS-ES). The inversion indicates a moderate decrease (ca. 20 %) in the average annual global fire and isoprene emissions, from 2028 Tg C in the a priori to 1653 Tg C for burned biomass, and from 343 to 272 Tg for isoprene fluxes. Those estimates are acknowledged to depend on the accuracy of formaldehyde data, as well as on the assumed fire emission factors and the oxidation mechanisms leading to HCHO production. Strongly decreased top-down fire fluxes (30-50 %) are inferred in the peak fire season in Africa and during years with strong a priori fluxes associated with forest fires in Amazonia (in 2005, 2007, and 2010), bushfires in Australia (in 2006 and 2011), and peat burning in Indonesia (in 2006 and 2009), whereas generally increased fluxes

  4. High-contrast en bloc staining of neuronal tissue for field emission scanning electron microscopy.

    Science.gov (United States)

    Tapia, Juan Carlos; Kasthuri, Narayanan; Hayworth, Kenneth J; Schalek, Richard; Lichtman, Jeff W; Smith, Stephen J; Buchanan, JoAnn

    2012-01-12

    Conventional heavy metal poststaining methods on thin sections lend contrast but often cause contamination. To avoid this problem, we tested several en bloc staining techniques to contrast tissue in serial sections mounted on solid substrates for examination by field emission scanning electron microscopy (FESEM). Because FESEM section imaging requires that specimens have higher contrast and greater electrical conductivity than transmission electron microscopy (TEM) samples, our technique uses osmium impregnation (OTO) to make the samples conductive while heavily staining membranes for segmentation studies. Combining this step with other classic heavy metal en bloc stains, including uranyl acetate (UA), lead aspartate, copper sulfate and lead citrate, produced clean, highly contrasted TEM and scanning electron microscopy (SEM) samples of insect, fish and mammalian nervous systems. This protocol takes 7-15 d to prepare resin-embedded tissue, cut sections and produce serial section images.

  5. Imaging plant nuclei and membrane-associated cytoskeleton by field emission scanning electron microscopy.

    Science.gov (United States)

    Fišerová, Jindřiška; Goldberg, Martin W

    2014-01-01

    Scanning electron microscopy (SEM) is a powerful technique that can image exposed surfaces in 3D. Modern scanning electron microscopes, with field emission electron sources and in-lens specimen chambers, achieve resolutions of better than 0.5 nm and thus offer views of ultrastructural details of subcellular structures or even macromolecular complexes. Obtaining a reliable image is, however, dependent on sample preparation methods that robustly but accurately preserve biological structures. In plants, exposing the object of interest may be difficult due to the existence of a cell wall. This protocol shows how to isolate plant nuclei for SEM imaging of the nuclear envelope and associated structures from both sides of the nuclear envelope in cultured cells as well as in leaf or root cells. Further, it provides a method for uncovering membrane-associated cytoskeletal structures.

  6. Measurements and Studies of Secondary Electron Emission of Diamond Amplified Photocathode

    Energy Technology Data Exchange (ETDEWEB)

    Wu,Q.

    2008-10-01

    The Diamond Amplified Photocathode (DAP) is a novel approach to generating electrons. By following the primary electron beam, which is generated by traditional electron sources, with an amplifier, the electron beam available to the eventual application is increased by 1 to 2 orders of magnitude in current. Diamond has a very wide band gap of 5.47eV which allows for a good negative electron affinity with simple hydrogenation, diamond can hold more than 2000MV/m field before breakdown. Diamond also provides the best rigidity among all materials. These two characters offer the capability of applying high voltage across very thin diamond film to achieve high SEY and desired emission phase. The diamond amplifier also is capable of handling a large heat load by conduction and sub-nanosecond pulse input. The preparation of the diamond amplifier includes thinning and polishing, cleaning with acid etching, metallization, and hydrogenation. The best mechanical polishing available can provide high purity single crystal diamond films with no less than 100 {micro}m thickness and <15 nm Ra surface roughness. The ideal thickness for 700MHz beam is {approx}30 {micro}m, which requires further thinning with RIE or laser ablation. RIE can achieve atomic layer removal precision and roughness eventually, but the time consumption for this procedure is very significant. Laser ablation proved that with <266nm ps laser beam, the ablation process on the diamond can easily achieve removing a few microns per hour from the surface and <100nm roughness. For amplifier application, laser ablation is an adequate and efficient process to make ultra thin diamond wafers following mechanical polishing. Hydrogenation will terminate the diamond surface with monolayer of hydrogen, and form NEA so that secondary electrons in the conduction band can escape into the vacuum. The method is using hydrogen cracker to strike hydrogen atoms onto the bare diamond surface to form H-C bonds. Two independent

  7. Sensitivity of Inferred Electron Temperature from X-ray Emission of NIF Cryogenic DT Implosions

    Energy Technology Data Exchange (ETDEWEB)

    Klem, Michael [Univ. of Dallas, Irving, TX (United States)

    2015-05-01

    The National Ignition Facility (NIF) at the Lawrence Livermore National Laboratory seeks to achieve thermonuclear ignition through inertial confinement fusion. The accurate assessment of the performance of each implosion experiment is a crucial step. Here we report on work to derive a reliable electron temperature for the cryogenic deuteriumtritium implosions completed on the NIF using the xray signal from the Ross filter diagnostic. These Xrays are dominated by bremsstrahlung emission. By fitting the xray signal measured through each of the individual Ross filters, the source bremsstrahlung spectrum can be inferred, and an electron temperature of the implosion hot spot inferred. Currently, each filter is weighted equally in this analysis. We present work quantifying the errors with such a technique and the results from investigating the contribution of each filter to the overall accuracy of the temperature inference. Using this research, we also compare the inferred electron temperature against other measured implosion quantities to develop a more complete understanding of the hotspot physics.

  8. A Pilot Study to Evaluate California's Fossil Fuel CO2 Emissions Using Atmospheric Observations

    Science.gov (United States)

    Graven, H. D.; Fischer, M. L.; Lueker, T.; Guilderson, T.; Brophy, K. J.; Keeling, R. F.; Arnold, T.; Bambha, R.; Callahan, W.; Campbell, J. E.; Cui, X.; Frankenberg, C.; Hsu, Y.; Iraci, L. T.; Jeong, S.; Kim, J.; LaFranchi, B. W.; Lehman, S.; Manning, A.; Michelsen, H. A.; Miller, J. B.; Newman, S.; Paplawsky, B.; Parazoo, N.; Sloop, C.; Walker, S.; Whelan, M.; Wunch, D.

    2016-12-01

    Atmospheric CO2 concentration is influenced by human activities and by natural exchanges. Studies of CO2 fluxes using atmospheric CO2 measurements typically focus on natural exchanges and assume that CO2 emissions by fossil fuel combustion and cement production are well-known from inventory estimates. However, atmospheric observation-based or "top-down" studies could potentially provide independent methods for evaluating fossil fuel CO2 emissions, in support of policies to reduce greenhouse gas emissions and mitigate climate change. Observation-based estimates of fossil fuel-derived CO2 may also improve estimates of biospheric CO2 exchange, which could help to characterize carbon storage and climate change mitigation by terrestrial ecosystems. We have been developing a top-down framework for estimating fossil fuel CO2 emissions in California that uses atmospheric observations and modeling. California is implementing the "Global Warming Solutions Act of 2006" to reduce total greenhouse gas emissions to 1990 levels by 2020, and it has a diverse array of ecosystems that may serve as CO2 sources or sinks. We performed three month-long field campaigns in different seasons in 2014-15 to collect flask samples from a state-wide network of 10 towers. Using measurements of radiocarbon in CO2, we estimate the fossil fuel-derived CO2 present in the flask samples, relative to marine background air observed at coastal sites. Radiocarbon (14C) is not present in fossil fuel-derived CO2 because of radioactive decay over millions of years, so fossil fuel emissions cause a measurable decrease in the 14C/C ratio in atmospheric CO2. We compare the observations of fossil fuel-derived CO2 to simulations based on atmospheric modeling and published fossil fuel flux estimates, and adjust the fossil fuel flux estimates in a statistical inversion that takes account of several uncertainties. We will present the results of the top-down technique to estimate fossil fuel emissions for our field

  9. Development of electronics and data acquisition system for independent calibration of electron cyclotron emission radiometer

    Energy Technology Data Exchange (ETDEWEB)

    Kumari, Praveena, E-mail: praveena@ipr.res.in; Raulji, Vismaysinh; Mandaliya, Hitesh; Patel, Jignesh; Siju, Varsha; Pathak, S.K.; Rajpal, Rachana; Jha, R.

    2016-11-15

    Highlights: • Indigenous development of an electronics and data acquisition system to digitize signals for a desired time and automatization of calibration process. • 16 bit DAQ board with form factor of 90 × 89 mm. • VHDL Codes written for generating control signals for PC104 Bus, ADC and RAM. • Averaging process is done in two ways single point averaging and additive averaging. - Abstract: Signal conditioning units (SCU) along with Multichannel Data acquisition system (DAS) are developed and installed for automatization and frequent requirement of absolute calibration of ECE radiometer system. The DAS is an indigenously developed economical system which is based on Single Board Computer (SBC). The onboard RAM memory of 64 K for each channel enables the DAS for simultaneous and continuous acquisition. A Labview based graphical user interface provides commands locally or remotely to acquire, process, plot and finally save the data in binary format. The microscopic signals received from radiometer are strengthened, filtered by SCU and acquired through DAS for the set time and at set sampling frequency. Stored data are processed and analyzed offline with Labview utility. The calibration process has been performed for two hours continuously at different sampling frequency (100 Hz to 1 KHz) at two set of temperature like hot body and the room temperature. The detailed hardware and software design and testing results are explained in the paper.

  10. Land-use and land-cover change carbon emissions between 1901 and 2012 constrained by biomass observations

    Science.gov (United States)

    Wei Li; Philippe Ciais; Shushi Peng; Chao Yue; Yilong Wang; Martin Thurner; Sassan S. Saatchi; Almut Arneth; Valerio Avitabile; Nuno Carvalhais; Anna B. Harper; Etsushi Kato; Charles Koven; Yi Y. Liu; Julia E. M. S. Nabel; Yude Pan; Julia Pongratz; Benjamin Poulter; Thomas A. M. Pugh; Maurizio Santoro; Stephen Sitch; Benjamin D. Stocker; Nicolas Viovy; Andy Wiltshire; Rasoul Yousefpour; Sönke Zaehle

    2017-01-01

    The use of dynamic global vegetation models (DGVMs) to estimate CO2 emissions from land-use and land-cover change (LULCC) offers a new window to account for spatial and temporal details of emissions and for ecosystem processes affected by LULCC. One drawback of LULCC emissions from DGVMs, however, is lack of observation constraint. Here, we...

  11. Observations of Low-Lying Electronic States of NiD, and Multi-Isotope Analysis

    Science.gov (United States)

    Abbasi, Mahdi; Shayesteh, Alireza; Crozet, Patrick; Ross, Amanda J.

    2017-06-01

    Resolved laser induced fluorescence spectra of NiD, recorded at Doppler resolution between 11500 and 18000 {cm^{-1}}, have defined some 200 term energies in two of the three strongly-interacting, low-lying ({X ^2Δ}, {W ^2Π} and {V ^2Σ^+}) states of NiD associated with an Ni{^+(3d^9})-D^- configuration. Our observations span v = 0 - 5 in the lowest spin-orbit component of the ground state, {X_1 ^2Δ_{5/2} }, v = 0 - 3 in {X_2 ^2Δ_{3/2} } and v = 0 - 1 in {W_1 ^2Π_{3/2} }, the lower component of the {W ^2Π } state. Spin-orbit and rotation-electronic interactions are strong in NiD. Large parity splittings are seen, due to interactions with the unobserved ^2Σ^+ state. We have attempted a global, multi-isotope fit to reproduce observed term energies up to 6000 {cm^{-1}} in NiD and ^{58,60,62}NiH, in an extension of the `Supermultiplet' model proposed by Gray and co-workers, because fits with NiD term energies alone failed to converge to sensible solutions. Dunham-type parameters have been used to represent the unperturbed X ^2Δ, W ^2Π and V ^2Σ^+ states, with off-diagonal matrix elements (treating spin-orbit, L- and S-uncoupling effects) based on Ni^+ atomic properties. Some electronic Born-Oppenheimer breakdown terms were included in the model. The spectra show emission from several excited states close to the unique level populated by the single-mode laser. Bands of collisionally-induced fluorescence identify three levels (A (Ω = 5/2) v = 1, E (Ω = 3/2) v = 1 and I (Ω = 3/2) v = 0) that have not been reported before. Gray, Li, Nelis, and Field, {J. Chem. Phys. 95, 7164 (1991)

  12. Estimating aerosol emissions by assimilating observed aerosol optical depth in a global aerosol model

    Directory of Open Access Journals (Sweden)

    N. Huneeus

    2012-05-01

    Full Text Available This study estimates the emission fluxes of a range of aerosol species and one aerosol precursor at the global scale. These fluxes are estimated by assimilating daily total and fine mode aerosol optical depth (AOD at 550 nm from the Moderate Resolution Imaging Spectroradiometer (MODIS into a global aerosol model of intermediate complexity. Monthly emissions are fitted homogenously for each species over a set of predefined regions. The performance of the assimilation is evaluated by comparing the AOD after assimilation against the MODIS observations and against independent observations. The system is effective in forcing the model towards the observations, for both total and fine mode AOD. Significant improvements for the root mean square error and correlation coefficient against both the assimilated and independent datasets are observed as well as a significant decrease in the mean bias against the assimilated observations. These improvements are larger over land than over ocean. The impact of the assimilation of fine mode AOD over ocean demonstrates potential for further improvement by including fine mode AOD observations over continents. The Angström exponent is also improved in African, European and dusty stations. The estimated emission flux for black carbon is 15 Tg yr−1, 119 Tg yr−1 for particulate organic matter, 17 Pg yr−1 for sea salt, 83 TgS yr−1 for SO2 and 1383 Tg yr−1 for desert dust. They represent a difference of +45 %, +40 %, +26 %, +13 % and −39 % respectively, with respect to the a priori values. The initial errors attributed to the emission fluxes are reduced for all estimated species.

  13. Self-amplified coherent spontaneous emission in a free electron laser with “quiet” bunches

    Directory of Open Access Journals (Sweden)

    V. A. Goryashko

    2013-03-01

    Full Text Available For a planar free electron laser (FEL configuration we study self-amplified coherent spontaneous emission driven by a gradient of the bunch current in the presence of different levels of noise in bunches. The longitudinal granularity of the electron bunch density originating from shot noise is maintained throughout the analysis. For the FEL model with the SwissFEL injector bunch parameters, we calculate the probability density distribution of the maximum power of the radiation pulses for different levels of shot noise. It turns out that the temporal coherence quickly increases as the noise level reduces. We also show that the FEL based on coherent spontaneous emission produces almost Fourier transform limited pulses. The analysis indicates that the time-bandwidth product is mainly determined by the bunch length and the interaction distance in an undulator. Calculations of the FEL characteristics for different rise times of the front of the current pulse are performed, and it is found that a reduced level of the power fluctuations is preserved for the bunch current pulse with a front duration up to several FEL wavelengths. We also propose a novel scheme that permits the formation of electron bunches with a reduced level of noise and a high gradient of the current at the bunch tail to enhance coherent spontaneous emission. The presented scheme uses effects of noise reduction and controlled microbunching instability and consists of a laser heater, a bunch compressor, and a shot noise suppression section. We show that shot noise reduction by 2 orders of magnitude in electron bunches produced by the SwissFEL injector can be achieved in a compact noise suppression section. The noise factor and microbunching gain of the overall proposed scheme with and without laser heater are estimated.

  14. Contribution of proton and electron precipitation to the observed electron concentration in October-November 2003 and September 2005

    Energy Technology Data Exchange (ETDEWEB)

    Verronen, P.T.; Andersson, M.E.; Kauristie, K.; Palmroth, M. [Finnish Meteorological Institute, Helsinki (Finland). Earth Observation; Kero, A. [Oulu Univ., Sodankylae (Finland). Sodankylae Geophysical Observatory; Enell, C.F. [EISCAT Scientific Association, Kiruna (Sweden); Wissing, J.M. [Osnabrueck Univ. (Germany). Inst. of Environmental Systems Research; Talaat, E.R. [Johns Hopkins Univ., Laurel, MD (United States). Applied Physics Lab.; Sarris, T.E. [Democritus Univ. of Thrace, Xanthi (Greece). Space Research Lab.; Armandillo, E. [European Space Agency, Nordwijk (Netherlands). ESTEC

    2015-01-01

    Understanding the altitude distribution of particle precipitation forcing is vital for the assessment of its atmospheric and climate impacts. However, the proportion of electron and proton forcing around the mesopause region during solar proton events is not always clear due to uncertainties in satellite-based flux observations. Here we use electron concentration observations of the European Incoherent Scatter Scientific Association (EISCAT) incoherent scatter radars located at Tromsoe (69.58 N, 19.23 E) to investigate the contribution of proton and electron precipitation to the changes taking place during two solar proton events. The EISCAT measurements are compared to the results from the SodankylaeIon and Neutral Chemistry Model (SIC). The proton ionization rates are calculated by two different methods - a simple energy deposition calculation and the Atmospheric Ionization Model Osnabrueck (AIMOS v1.2), the latter providing also the electron ionization rates. Our results show that in general the combination of AIMOS and SIC is able to reproduce the observed electron concentration within 50% when both electron and proton forcing is included. Electron contribution is dominant above 90 km, and can contribute significantly also in the upper mesosphere especially during low or moderate proton forcing. In the case of strong proton forcing, the AIMOS electron ionization rates seem to suffer from proton contamination of satellite-based flux data. This leads to overestimation of modelled electron concentrations by up to 90% between 75-90 km and up to 100-150% at 70-75 km. Above 90 km, the model bias varies significantly between the events. Although we cannot completely rule out EISCAT data issues, the difference is most likely a result of the spatio-temporal fine structure of electron precipitation during individual events that cannot be fully captured by sparse in situ flux (point) measurements, nor by the statistical AIMOS model which is based upon these observations

  15. Modeling the total electron content observations above Ascension Island

    Energy Technology Data Exchange (ETDEWEB)

    Anderson, D.N.; Klobuchar, J.A.

    1983-10-01

    Recent Faraday rotation (136 MHz) measurements between Ascension Island (8/sup 0/ S geographic latitude; 345/sup 0/ E geographic longitude; 15/sup 0/ S. dip latitude) and the Sirio satellite (azimuth 0/sup 0/, elevation 80/sup 0/)= reveal two characteristic features associated with the undisturbed ambient ionosphere: a late afternoon decrease in TEC followed by a postsunset enhancement that lasts for two to three hours. We theoretically investigate the ambient ionosphere above Ascension Island by numerically solving the time-dependent plasma continuity equation, including the effects of ionization production by solar ultraviolet radiation, loss through charge exchange and transport by diffusion, E-bar x B-bar drift and neutral wind (both zonal and meridional components) appropriate for an equinoctial, solar cycle maximum period. It is found that the postsunset enhancement in upward E-bar x B-bar drift, which is a characteristic feature observed by the Jicamarca incoherent scatter radar facility during solar cycle maximum periods, is primarily responsible for the postsunset increase in TEC observed at Ascension Island between 1900 and 2300 LT. The late afternoon decrease in TEC is caused by an increase in the poleward neutral wind velocity, which lowers the F layer into a higher loss rate region. Inclusion of the meridional wind not only reproduces the observed decrease but also modulates the postsunset peak in TEC so that it is in much better agreement with the observed values. Calculated north-south asymmetries in TEC caused by a zonal wind component are also discussed.

  16. Electron densities in quiescent prominences derived from eclipse observations

    Czech Academy of Sciences Publication Activity Database

    Jejčič, S.; Heinzel, Petr

    2009-01-01

    Roč. 254, č. 1 (2009), s. 89-100 ISSN 0038-0938 Grant - others:EU(XE) ESA-PECS project No. 98030 Institutional research plan: CEZ:AV0Z10030501 Keywords : prominences quiescent * eclipse observations * visible spectrum Subject RIV: BN - Astronomy, Celestial Mechanics, Astrophysics Impact factor: 3.628, year: 2009

  17. Observation of two successive quantum supershells in a 15 000-electron fermionic system

    Energy Technology Data Exchange (ETDEWEB)

    Pellarin, M.; Cottancin, E.; Baguenard, B.; Lerme, J.; Vialle, J.L.; Broyer, M. [Laboratoire de Spectrometrie Ionique et Moleculaire, CNRS Universite Lyon 1, Batiment 205, 43 Boulevard du 11 Novembre 1918, 69622 Villeurbanne Cedex (France)

    1995-12-15

    The electronic shell structure of gallium clusters has been investigated up to nearly 15 000 valence electrons and two successive supershell nodes are observed. The location of these nodes around 2500 and 7500 electrons, respectively, is interpreted in the framework of the jellium model by introducing the ion pseudopotential and a surface softness for the ionic density.

  18. Active vacuum brazing of CNT films to metal substrates for superior electron field emission performance.

    Science.gov (United States)

    Longtin, Rémi; Ramon Sanchez-Valencia, Juan; Shorubalko, Ivan; Furrer, Roman; Hack, Erwin; Elsener, Hansrudolf; Gröning, Oliver; Greenwood, Paul; Rupesinghe, Nalin; Teo, Kenneth; Leinenbach, Christian; Gröning, Pierangelo

    2015-02-01

    The joining of macroscopic films of vertically aligned multiwalled carbon nanotubes (CNTs) to titanium substrates is demonstrated by active vacuum brazing at 820 °C with a Ag-Cu-Ti alloy and at 880 °C with a Cu-Sn-Ti-Zr alloy. The brazing methodology was elaborated in order to enable the production of highly electrically and thermally conductive CNT/metal substrate contacts. The interfacial electrical resistances of the joints were measured to be as low as 0.35 Ω. The improved interfacial transport properties in the brazed films lead to superior electron field-emission properties when compared to the as-grown films. An emission current of 150 μA was drawn from the brazed nanotubes at an applied electric field of 0.6 V μm-1. The improvement in electron field-emission is mainly attributed to the reduction of the contact resistance between the nanotubes and the substrate. The joints have high re-melting temperatures up to the solidus temperatures of the alloys; far greater than what is achievable with standard solders, thus expanding the application potential of CNT films to high-current and high-power applications where substantial frictional or resistive heating is expected.

  19. Observations of artificial and natural optical emissions at the HAARP facility

    Directory of Open Access Journals (Sweden)

    T. Pedersen

    2008-05-01

    Full Text Available Extensive optical observations have been carried out at the High Frequency Active Auroral Research Program (HAARP ionospheric heating facility since it began operations in 1999. A number of modern optical diagnostic instruments are hosted at remote sites as well as the main transmitter facility, which has recently been expanded from the initial 960 kW prototype configuration to its full 3.6 MW design capability. Upgrades to optical diagnostics have allowed a number of interesting new observations to be made at the 960 kW power level since 2004. Systematic beam-swinging experiments generating quantifiable levels of optical emission at various regions in the sky for the first time clearly show that emission intensity is very sensitive to distance from the magnetic zenith, and drops off rapidly at about 15° zenith angle in directions other than magnetic south. High temporal resolution measurements of emissions in the 557.7 nm green line at start-up and in short transmitter pulses demonstrate that localized irregularities are preferentially excited in the initial seconds of heating, with evolution into a more homogenous spot occurring over a period of about 1 min. High-quality emission altitude profiles at both 630.0 and 557.7 nm have recently been isolated from side-looking data, spanning an altitude extent of over 200 km, which has allowed determination of the effective lifetime of O (1D over an unprecedented altitude range. An innovative automated remote imager network utilizing low-cost mirror optics has been designed and deployed to make such measurements routinely. Observations of natural optical emissions at the site have revealed the common presence of highly structured but faint co-rotating subauroral precipitation that acts to suppress excitation of artificial F region optical emissions in areas of active precipitation. The observed spatial modulation of artificial optical emissions by structured precipitation is consistent

  20. Electron Microscopy Observation of Biomineralization within Wood Tissues of Kurogaki

    Directory of Open Access Journals (Sweden)

    Kazue Tazaki

    2017-07-01

    Full Text Available Interactions between minerals and microorganisms play a crucial role in living wood tissues. However, living wood tissues have never been studied in the field. Fortunately, we found several kurogaki (black persimmon; Diospyros kaki trees at Tawara in Kanazawa, Ishikawa, Japan. Here, we report the characterization of kurogaki based on scanning electron microscopy equipped with energy-dispersive spectroscopy (SEM-EDS and transmission electron microscopy (TEM, associated with inductively coupled plasma-mass spectrometry (ICP-MS analyses, X-ray fluorescence analyses (XRF and X-ray powder diffraction (XRD analyses. This study aims to illustrate the ability of various microorganisms associated with biominerals within wood tissues of kurogaki, as shown by SEM-EDS elemental content maps and TEM images. Kurogaki grows very slowly and has extremely hard wood, known for its striking black and beige coloration, referred to as a “peacock pattern”. However, the scientific data for kurogaki are very limited. The black “peacock pattern” of the wood mainly comprises cellulose and high levels of crystal cristobalite. As per the XRD results, the black taproot contains mineralized 7 Å clays (kaolinite, cellulose, apatite and cristobalite associated with many microorganisms. The chemical compositions of the black and beige portions of the black persimmon tree were obtained by ICP-MS analyses. Particular elements such as abundant Ca, Mg, K, P, Mn, Ba, S, Cl, Fe, Na, and Al were concentrated in the black region, associated with Pb and Sr elements. SEM-EDS semi-qualitative analyses of kurogaki indicated an abundance of P and Ca in microorganisms in the black region, associated with Pb, Sr, S, Mn, and Mg elements. On the other hand, XRF and XRD mineralogical data showed that fresh andesite, weathered andesite, and the soils around the roots of kurogaki correlate with biomineralization of the black region in kurogaki roots, showing clay minerals (kaolinite and

  1. Spatially resolved band alignments at Au-hexadecanethiol monolayer-GaAs(001) interfaces by ballistic electron emission microscopy

    Energy Technology Data Exchange (ETDEWEB)

    Junay, A.; Guézo, S., E-mail: sophie.guezo@univ-rennes1.fr; Turban, P.; Delhaye, G.; Lépine, B.; Tricot, S.; Ababou-Girard, S.; Solal, F. [Département Matériaux-Nanosciences, Institut de Physique de Rennes, UMR 6251, CNRS-Université de Rennes 1, Campus de Beaulieu, Bât 11E, 35042 Rennes Cedex (France)

    2015-08-28

    We study structural and electronic inhomogeneities in Metal—Organic Molecular monoLayer (OML)—semiconductor interfaces at the sub-nanometer scale by means of in situ Ballistic Electron Emission Microscopy (BEEM). BEEM imaging of Au/1-hexadecanethiols/GaAs(001) heterostructures reveals the evolution of pinholes density as a function of the thickness of the metallic top-contact. Using BEEM in spectroscopic mode in non-short-circuited areas, local electronic fingerprints (barrier height values and corresponding spectral weights) reveal a low-energy tunneling regime through the insulating organic monolayer. At higher energies, BEEM evidences new conduction channels, associated with hot-electron injection in the empty molecular orbitals of the OML. Corresponding band diagrams at buried interfaces can be thus locally described. The energy position of GaAs conduction band minimum in the heterostructure is observed to evolve as a function of the thickness of the deposited metal, and coherently with size-dependent electrostatic effects under the molecular patches. Such BEEM analysis provides a quantitative diagnosis on metallic top-contact formation on organic molecular monolayer and appears as a relevant characterization for its optimization.

  2. Summary of EC-17: the 17th Joint Workshop on Electron Cyclotron Emission and Electron Cyclotron Resonance Heating (Deurne, The Netherlands, 7-10 May 2012)

    NARCIS (Netherlands)

    Westerhof, E.; Austin, M. E.; Kubo, S.; Lin-Liu, Y. R.; Plaum, B.

    2013-01-01

    An overview is given of the papers presented at the 17th Joint Workshop on Electron Cyclotron Emission (ECE) and Electron Cyclotron Resonance Heating (ECRH). The meeting covered all aspects of the research field ranging from theory to enabling technologies. From the workshop, advanced control by

  3. On radiation emission from a microbunched beam with wavefront tilt and its experimental observation

    Energy Technology Data Exchange (ETDEWEB)

    Geloni, Gianluca [European XFEL GmbH, Hamburg (Germany); Kocharyan, Vitali; Saldin, Evgeni [Deutsches Elektronen-Synchrotron (DESY), Hamburg (Germany)

    2017-06-15

    In this paper we compare experimental observations and theory of radiation emission from a microbunched beam with microbunching wavefront tilt with respect to the direction of motion. The theory refers to the work of T. Tanaka, H. Kitamura, and T. Shintake (2004), which predicts, in this case, exponential suppression of coherent radiation along the kicked direction. The observations refer to a recent experiment performed at the LCLS, where a microbunched beam was kicked by a bend and sent to a radiator undulator. The experiment resulted in the emission of strong coherent radiation that had its maximum along the kicked direction of motion, when the undulator parameter was detuned to a value larger than the nominal one. We first analyze the theory in detail, and we confirm the correctness of its derivation according to the conventional theory of radiation emission from charged particles. Subsequently, we look for possible peculiarities in the experiment, which may not be modeled by the theory. We show that only spurious effects are not accounted for. We conclude that the experiment defies explanation in terms of the conventional theory of radiation emission.

  4. Non-thermal plasma mills bacteria: Scanning electron microscopy observations

    Energy Technology Data Exchange (ETDEWEB)

    Lunov, O., E-mail: lunov@fzu.cz; Churpita, O.; Zablotskii, V.; Jäger, A.; Dejneka, A. [Institute of Physics AS CR, Prague 18221 (Czech Republic); Deyneka, I. G.; Meshkovskii, I. K. [St. Petersburg State University of Information Technologies, Mechanics and Optics, St. Petersburg 197101 (Russian Federation); Syková, E. [Institute of Experimental Medicine AS CR, Prague 14220 (Czech Republic); Kubinová, Š. [Institute of Physics AS CR, Prague 18221 (Czech Republic); Institute of Experimental Medicine AS CR, Prague 14220 (Czech Republic)

    2015-02-02

    Non-thermal plasmas hold great promise for a variety of biomedical applications. To ensure safe clinical application of plasma, a rigorous analysis of plasma-induced effects on cell functions is required. Yet mechanisms of bacteria deactivation by non-thermal plasma remain largely unknown. We therefore analyzed the influence of low-temperature atmospheric plasma on Gram-positive and Gram-negative bacteria. Using scanning electron microscopy, we demonstrate that both Gram-positive and Gram-negative bacteria strains in a minute were completely destroyed by helium plasma. In contrast, mesenchymal stem cells (MSCs) were not affected by the same treatment. Furthermore, histopathological analysis of hematoxylin and eosin–stained rat skin sections from plasma–treated animals did not reveal any abnormalities in comparison to control ones. We discuss possible physical mechanisms leading to the shred of bacteria under non-thermal plasma irradiation. Our findings disclose how helium plasma destroys bacteria and demonstrates the safe use of plasma treatment for MSCs and skin cells, highlighting the favorability of plasma applications for chronic wound therapy.

  5. Observations of electron cloud phenomena at PETRA III

    CERN Document Server

    Wanzenberg, R

    2013-01-01

    PETRA III is a third generation synchrotron radiation facility at DESY, which is presently operated with positron beams. Regular user operation started in mid 2010 after a commissioning phase which began in April 2009. The design current of 100 mA has been achieved but with different number of bunches and bunch to bunch distances than originally foreseen since a strong vertical emittance growth was observed for the design bunch filling pattern with 960 bunches. During machine studies different bunch filling patterns have been tested. In 2012 two scrubbing runs with 480 bunches and a bunch to bunch spacing of 16 ns have been done. The recent measurements indicate that the scrubbing runs have mitigated the emittance growth. Furthermore conditioning effects have been observed during the user runs in 2011. The results from the measured emittances and tune spectra are reported.

  6. CORONAS-F observation of gamma-ray emission from the solar flare on 2003 October 29

    Science.gov (United States)

    Kurt, Victoria G.; Yushkov, Boris Yu.; Galkin, Vladimir I.; Kudela, Karel; Kashapova, Larisa K.

    2017-10-01

    Appreciable hard X-ray (HXR) and gamma-ray emissions in the 0.04-150 MeV energy range associated with the 2003 October 29 solar flare (X10/3B) were observed at 20:38-20:58 UT by the SONG instrument onboard the CORONAS-F mission. To restore flare gamma-ray spectra we fitted the SONG energy loss spectra with a three-component model of the incident spectrum: (1) a power law in energy, assumed to be due to electron bremsstrahlung; (2) a broad continuum produced by prompt nuclear de-excitation gamma-lines; and (3) a broad gamma-line generated from pion-decay. We also restored spectra from the RHESSI data, compared them with the SONG spectra and found a reasonable agreement between these spectra in the 0.1-10 MeV energy range. The pion-decay emission was observed from 20:44:20 UT and had its maximum at 20:48-20:51 UT. The power-law spectral index of accelerated protons estimated from the ratio between intensities of different components of gamma rays changed with time. The hardest spectrum with a power-law index S = -3.5 - 3.6 was observed at 20:48-20:51 UT. Time histories of the pion-decay emission and proton spectrum were compared with changes of the locations of flare energy release as shown by RHESSI hard X-ray images and remote and remote Hα brightenings. An apparent temporal correlation between processes of particle acceleration and restructuring of flare magnetic field was found. In particular, the protons were accelerated to subrelativistic energies after radical change of the character of footpoint motion from a converging motion to a separation motion.

  7. Development of an ultrafast electron source based on a cold-field emission gun for ultrafast coherent TEM

    Science.gov (United States)

    Caruso, Giuseppe Mario; Houdellier, Florent; Abeilhou, Pierre; Arbouet, Arnaud

    2017-07-01

    We report on the design of a femtosecond laser-driven electron source for ultrafast coherent transmission electron microscopy. The proposed architecture allows introducing an ultrafast laser beam inside the cold field emission source of a commercial TEM, aligning and focusing the laser spot on the apex of the nanoemitter. The modifications of the gun assembly do not deteriorate the performances of the electron source in conventional DC mode and allow easy switching between the conventional and ultrafast laser-driven emission modes. We describe here this ultrafast electron source and discuss its properties.

  8. Maven Observations of Electron-Induced Whistler Mode Waves in the Martian Magnetosphere

    Science.gov (United States)

    Harada, Y.; Andersson, L.; Fowler, C. M.; Mitchell, D. L.; Halekas, J. S.; Mazelle, C.; Espley, J.; DiBraccio, G. A.; McFadden, J. P.; Brian, D. A.; hide

    2016-01-01

    We report on narrowband electromagnetic waves at frequencies between the local electron cyclotron and lower hybrid frequencies observed by the Mars Atmosphere and Volatile EvolutioN (MAVEN) spacecraft in the Martian induced magnetosphere. The peaked electric field wave spectra below the electron cyclotron frequency were first observed by Phobos-2 in the Martian magnetosphere, but the lack of magnetic field wave data prevented definitive identification of the wave mode and their generation mechanisms remain unclear. Analysis of electric and magnetic field wave spectra obtained by MAVEN demonstrates that the observed narrowband waves have properties consistent with the whistler mode. Linear growth rates computed from the measured electron velocity distributions suggest that these whistler mode waves can be generated by cyclotron resonance with anisotropic electrons. Large electron anisotropy in the Martian magnetosphere is caused by absorption of parallel electrons by the collisional atmosphere. The narrowband whistler mode waves and anisotropic electrons are observed on both open and closed field lines and have similar spatial distributions in MSO and planetary coordinates. Some of the waves on closed field lines exhibit complex frequency-time structures such as discrete elements of rising tones and two bands above and below half the electron cyclotron frequency. These MAVEN observations indicate that whistler mode waves driven by anisotropic electrons, which are commonly observed in intrinsic magnetospheres and at unmagnetized airless bodies, are also present at Mars. The wave-induced electron precipitation into the Martian atmosphere should be evaluated in future studies.

  9. Measurement of turbulent electron temperature fluctuations on the ASDEX Upgrade tokamak using correlated electron cyclotron emission

    Energy Technology Data Exchange (ETDEWEB)

    Freethy, S. J., E-mail: simon.freethy@ipp.mpg.de [Max Planck Institute for Plasma Physics, 85748 Garching (Germany); Plasma Science and Fusion Center, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139 (United States); Conway, G. D.; Happel, T.; Köhn, A. [Max Planck Institute for Plasma Physics, 85748 Garching (Germany); Classen, I.; Vanovac, B. [FOM Institute DIFFER, 5612 AJ Eindhoven (Netherlands); Creely, A. J.; White, A. E. [Plasma Science and Fusion Center, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139 (United States)

    2016-11-15

    Turbulent temperature fluctuations are measured on the ASDEX Upgrade tokamak using pairs of closely spaced, narrow-band heterodyne radiometer channels and a standard correlation technique. The pre-detection spacing and bandwidth of the radiometer channel pairs is chosen such that they are physically separated less than a turbulent correlation length, but do not overlap. The radiometer has 4 fixed filter frequency channels and two tunable filter channels for added flexibility in the measurement position. Relative temperature fluctuation amplitudes are observed in a helium plasma to be δT/T = (0.76 ± 0.02)%, (0.67 ± 0.02)%, and (0.59 ± 0.03)% at normalised toroidal flux radius of ρ{sub tor} = 0.82, 0.75, and 0.68, respectively.

  10. Atomic imaging using secondary electrons in a scanning transmission electron microscope: Experimental observations and possible mechanisms

    Energy Technology Data Exchange (ETDEWEB)

    Inada, H. [Brookhaven National Laboratory, Upton, NY 11973 (United States); Hitachi High Technologies Corp., Ibaraki (Japan); Su, D. [Brookhaven National Laboratory, Upton, NY 11973 (United States); Egerton, R.F. [University of Alberta, Edmonton (Canada); Konno, M. [Hitachi High Technologies Corp., Ibaraki (Japan); Wu, L.; Ciston, J.; Wall, J. [Brookhaven National Laboratory, Upton, NY 11973 (United States); Zhu, Y., E-mail: zhu@bnl.gov [Brookhaven National Laboratory, Upton, NY 11973 (United States)

    2011-06-15

    We report detailed investigation of high-resolution imaging using secondary electrons (SE) with a sub-nanometer probe in an aberration-corrected transmission electron microscope, Hitachi HD2700C. This instrument also allows us to acquire the corresponding annular dark-field (ADF) images both simultaneously and separately. We demonstrate that atomic SE imaging is achievable for a wide range of elements, from uranium to carbon. Using the ADF images as a reference, we studied the SE image intensity and contrast as functions of applied bias, atomic number, crystal tilt, and thickness to shed light on the origin of the unexpected ultrahigh resolution in SE imaging. We have also demonstrated that the SE signal is sensitive to the terminating species at a crystal surface. A possible mechanism for atomic-scale SE imaging is proposed. The ability to image both the surface and bulk of a sample at atomic-scale is unprecedented, and can have important applications in the field of electron microscopy and materials characterization. -- Research highlights: {yields} Atomic imaging using secondary electrons in an aberration-corrected electron microscope. {yields} High-resolution secondary electron imaging mechanism. {yields} Image contrast quantification and as functions of imaging conditions. {yields} Simultaneous acquisition of atomic images from surface and bulk.

  11. MAVEN observations of gyrotropic electron distributions upstream of Mars bow shock

    Science.gov (United States)

    Meziane, Karim; McFadden, James; Hamza, A. M.; Mazelle, Christian; Jakosky, Bruce; Mitchell, David; Halekas, Jasper; Espley, Jared; Connerney, J. E. D.

    2016-07-01

    Recent observations upstream from the Martian bow shock by the MAVEN Solar Wind Electron Analyzer (SWEA) experiment are presented. Flux enhancements of electrons with energies 70-400 eV are always observed when MAVEN spacecraft is magnetically connected to the shock. A detailed examination of the pitch angle distribution shows that the enhanced fluxes are associated with electrons moving away from Mars. In the full 3-D angular distribution, the electrons appear in an 'annulus' centered along the IMF direction. Moreover, the gyrotropic character is observed over a large range of shock geometry from quasi-parallel to quasi-perpendicular. These signatures in the electron distribution function strongly suggest that the reflection off the shock is the main mechanism for the production of Martian foreshock electrons. A quantitative analysis of electron distributions is carried out in order to probe the characteristics of the Martian bow shock.

  12. Improvement on the visualization of cytoskeletal structures of protozoan parasites using high-resolution field emission scanning electron microscopy (FESEM).

    Science.gov (United States)

    Sant'Anna, Celso; Campanati, Loraine; Gadelha, Catarina; Lourenço, Daniela; Labati-Terra, Letícia; Bittencourt-Silvestre, Joana; Benchimol, Marlene; Cunha-e-Silva, Narcisa Leal; De Souza, Wanderley

    2005-07-01

    The association of high resolution field emission scanning electron microscopy (FESEM), with a more efficient system of secondary electron (SE) collection and in-lens specimen position, provided a great improvement in the specimen's topographical contrast and in the generation of high-resolution images. In addition, images obtained with the use of the high-resolution backscattered electrons (BSE) detector provided a powerful tool for immunocytochemical analysis of biological material. In this work, we show the contribution of the FESEM to the detailed description of cytoskeletal structures of the protozoan parasites Herpetomonas megaseliae, Trypanosoma brucei and Giardia lamblia. High-resolution images of detergent extracted H. megaseliae and T. brucei showed the profile of the cortical microtubules, also known as sub-pellicular microtubules (SPMT), and protein bridges cross-linking them. Also, it was possible to visualize fine details of the filaments that form the lattice-like structure of the paraflagellar rod (PFR) and its connection with the axoneme. In G. lamblia, it was possible to observe the intricate structure of the adhesive disk, funis (a microtubular array) and other cytoskeletal structures poorly described previously. Since most of the stable cytoskeletal structures of this protozoan rely on tubulin, we used the BSE images to accurately map immunolabeled tubulin in its cytoskeleton. Our results suggest that the observation of detergent extracted parasites using FESEM associated to backscattered analysis of immunolabeled specimens represents a new approach for the study of parasite cytoskeletal elements and their protein associations.

  13. Drawing the geometry of 3d transition metal-boron pairs in silicon from electron emission channeling experiments

    CERN Document Server

    Silva, Daniel; Wahl, Ulrich; Martins Correia, Joao; Augustyns, Valerie; De Lemos Lima, Tiago Abel; Granadeiro Costa, Angelo Rafael; David Bosne, Eric; Castro Ribeiro Da Silva, Manuel; Esteves De Araujo, Araujo Joao Pedro; Da Costa Pereira, Lino Miguel

    2016-01-01

    Although the formation of transition metal-boron pairs is currently well established in silicon processing, the geometry of these complexes is still not completely understood. We investigated the lattice location of the transition metals manganese, iron, cobalt and nickel in n- and p+-type silicon by means of electron emission channeling. For manganese, iron and cobalt, we observed an increase of sites near the ideal tetrahedral interstitial position by changing the doping from n- to p+-type Si. Such increase was not observed for Ni. We ascribe this increase to the formation of pairs with boron, driven by Coulomb interactions, since the majority of iron, manganese and cobalt is positively charged in p+-type silicon while Ni is neutral. We propose that breathing mode relaxation around the boron ion within the pair causes the observed displacement from the ideal tetrahedral interstitial site. We discuss the application of the emission channeling technique in this system and, in particular, how it provides insi...

  14. Sensitivity of wetland methane emissions to model assumptions: application and model testing against site observations

    Directory of Open Access Journals (Sweden)

    L. Meng

    2012-07-01

    Full Text Available Methane emissions from natural wetlands and rice paddies constitute a large proportion of atmospheric methane, but the magnitude and year-to-year variation of these methane sources are still unpredictable. Here we describe and evaluate the integration of a methane biogeochemical model (CLM4Me; Riley et al., 2011 into the Community Land Model 4.0 (CLM4CN in order to better explain spatial and temporal variations in methane emissions. We test new functions for soil pH and redox potential that impact microbial methane production in soils. We also constrain aerenchyma in plants in always-inundated areas in order to better represent wetland vegetation. Satellite inundated fraction is explicitly prescribed in the model, because there are large differences between simulated fractional inundation and satellite observations, and thus we do not use CLM4-simulated hydrology to predict inundated areas. A rice paddy module is also incorporated into the model, where the fraction of land used for rice production is explicitly prescribed. The model is evaluated at the site level with vegetation cover and water table prescribed from measurements. Explicit site level evaluations of simulated methane emissions are quite different than evaluating the grid-cell averaged emissions against available measurements. Using a baseline set of parameter values, our model-estimated average global wetland emissions for the period 1993–2004 were 256 Tg CH4 yr−1 (including the soil sink and rice paddy emissions in the year 2000 were 42 Tg CH4 yr−1. Tropical wetlands contributed 201 Tg CH4 yr−1, or 78% of the global wetland flux. Northern latitude (>50 N systems contributed 12 Tg CH4 yr−1. However, sensitivity studies show a large range (150–346 Tg CH4 yr−1 in predicted global methane emissions (excluding emissions from rice paddies. The large range is

  15. Electron emission of cathode holder of vacuum diode of an intense electron-beam accelerator and its effect on the output voltage

    Directory of Open Access Journals (Sweden)

    Xin-Bing Cheng

    2011-04-01

    Full Text Available The vacuum diode which is used to generate relativistic electron beams is one of the most important parts of a pulsed-power modulator. In this paper, the electron emission of cathode holder of a vacuum diode and its effect on the output voltage is investigated by experiments on an intense electron-beam accelerator with 180 ns full width at half maximum and 200–500 kV output voltage. First, the field emission is analyzed and the electric field of the vacuum chamber is calculated. Then, the flatness of the output voltage is discussed before and after adding an insulation plate when a water load is used. It is found that the electron emission at the edges of the cathode holder is the main reason to cause the change of the flatness. Last, a piece of polyester film is used as a target to further show the electron emission of the cathode holder. This analysis shows that decreasing the electron emission of the cathode holder in such a pulse power modulator could be a good way to improve the quality of the output voltage.

  16. Filtering of the interstellar dust flow near the heliopause: the importance of secondary electron emission for the grain charging

    OpenAIRE

    Kimura, Hiroshi; Mann, Ingrid

    1999-01-01

    The deflection of interstellar dust grains in the magnetic field near the heliopause depends on their surface electric charge. We study the electric charging of the grains with emphasis on the secondary electron emission because of its importance in the hot plasma environment near the heliopause. We correct previous models of the secondary electron emission that overestimate the electric charge of dust near the heliopause. Our model calculations of the grain charge, when combined with results...

  17. Direct observation of radiation-belt electron acceleration from electron-volt energies to megavolts by nonlinear whistlers.

    Science.gov (United States)

    Mozer, F S; Agapitov, O; Krasnoselskikh, V; Lejosne, S; Reeves, G D; Roth, I

    2014-07-18

    The mechanisms for accelerating electrons from thermal to relativistic energies in the terrestrial magnetosphere, on the sun, and in many astrophysical environments have never been verified. We present the first direct observation of two processes that, in a chain, cause this acceleration in Earth's outer radiation belt. The two processes are parallel acceleration from electron-volt to kilovolt energies by parallel electric fields in time-domain structures (TDS), after which the parallel electron velocity becomes sufficiently large for Doppler-shifted upper band whistler frequencies to be in resonance with the electron gyration frequency, even though the electron energies are kilovolts and not hundreds of kilovolts. The electrons are then accelerated by the whistler perpendicular electric field to relativistic energies in several resonant interactions. TDS are packets of electric field spikes, each spike having duration of a few hundred microseconds and containing a local parallel electric field. The TDS of interest resulted from nonlinearity of the parallel electric field component in oblique whistlers and consisted of ∼ 0.1 msec pulses superposed on the whistler waveform with each such spike containing a net parallel potential the order of 50 V. Local magnetic field compression from remote activity provided the free energy to drive the two processes. The expected temporal correlations between the compressed magnetic field, the nonlinear whistlers with their parallel electric field spikes, the electron flux and the electron pitch angle distributions were all observed.

  18. Study of a high power hydrogen beam diagnostic based on secondary electron emission

    Energy Technology Data Exchange (ETDEWEB)

    Sartori, E., E-mail: emanuele.sartori@igi.cnr.it [Consorzio RFX (CNR, ENEA, INFN, UNIPD, Acciaierie Venete SpA), Corso Stati Uniti 4, 35127 Padova (Italy); Department of Management and Engineering, University di Padova strad. S. Nicola 3, 36100 Vicenza (Italy); Panasenkov, A. [NRC, Kurchatov Institute, 1, Kurchatov Sq, Moscow 123182 (Russian Federation); Veltri, P. [Consorzio RFX (CNR, ENEA, INFN, UNIPD, Acciaierie Venete SpA), Corso Stati Uniti 4, 35127 Padova (Italy); INFN-LNL, viale dell’Università n. 2, 35020 Legnaro (Italy); Serianni, G.; Pasqualotto, R. [Consorzio RFX (CNR, ENEA, INFN, UNIPD, Acciaierie Venete SpA), Corso Stati Uniti 4, 35127 Padova (Italy)

    2016-11-15

    In high power neutral beams for fusion, beam uniformity is an important figure of merit. Knowing the transverse power profile is essential during the initial phases of beam source operation, such as those expected for the ITER heating neutral beam (HNB) test facility. To measure it a diagnostic technique is proposed, based on the collection of secondary electrons generated by beam-surface and beam-gas interactions, by an array of positively biased collectors placed behind the calorimeter tubes. This measurement showed in the IREK test stand good proportionality to the primary beam current. To investigate the diagnostic performances in different conditions, we developed a numerical model of secondary electron emission, induced by beam particle impact on the copper tubes, and reproducing the cascade of secondary emission caused by successive electron impacts. The model is first validated against IREK measurements. It is then applied to the HNB case, to assess the locality of the measurement, the proportionality to the beam current density, and the influence of beam plasma.

  19. Low-dimensional models for the estimation of anthropogenic CO2 emissions from atmospheric observ